diff --git a/lib/lob/models/bank_account.rb b/lib/lob/models/bank_account.rb
index b0cc169..9c9c33a 100755
--- a/lib/lob/models/bank_account.rb
+++ b/lib/lob/models/bank_account.rb
@@ -257,7 +257,7 @@ def list_invalid_properties
         invalid_properties.push("invalid value for \"id\", must conform to the pattern #{pattern}.")
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !@signature_url.nil? && @signature_url !~ pattern
         invalid_properties.push("invalid value for \"signature_url\", must conform to the pattern #{pattern}.")
       end
@@ -293,7 +293,7 @@ def valid?
       return false if @signatory.to_s.length > 30
       return false if @id.nil?
       return false if @id !~ Regexp.new(/^bank_[a-zA-Z0-9]+$/)
-      return false if !@signature_url.nil? && @signature_url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      return false if !@signature_url.nil? && @signature_url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       return false if @date_created.nil?
       return false if @date_modified.nil?
       return false if @object.nil?
@@ -392,7 +392,7 @@ def id=(id)
     # Custom attribute writer method with validation
     # @param [Object] signature_url Value to be assigned
     def signature_url=(signature_url)
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !signature_url.nil? && signature_url !~ pattern
         fail ArgumentError, "invalid value for \"signature_url\", must conform to the pattern #{pattern}."
       end
diff --git a/lib/lob/models/check.rb b/lib/lob/models/check.rb
index ea2b285..8f1dfd5 100755
--- a/lib/lob/models/check.rb
+++ b/lib/lob/models/check.rb
@@ -402,7 +402,7 @@ def list_invalid_properties
         invalid_properties.push('invalid value for "url", url cannot be nil.')
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if @url !~ pattern
         invalid_properties.push("invalid value for \"url\", must conform to the pattern #{pattern}.")
       end
@@ -447,7 +447,7 @@ def valid?
       return false if !@check_bottom_template_version_id.nil? && @check_bottom_template_version_id !~ Regexp.new(/^vrsn_[a-zA-Z0-9]+$/)
       return false if !@attachment_template_version_id.nil? && @attachment_template_version_id !~ Regexp.new(/^vrsn_[a-zA-Z0-9]+$/)
       return false if @url.nil?
-      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       return false if @carrier.nil?
       carrier_validator = EnumAttributeValidator.new('String', ["USPS"])
       return false unless carrier_validator.valid?(@carrier)
@@ -605,7 +605,7 @@ def url=(url)
         fail ArgumentError, 'url cannot be nil'
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if url !~ pattern
         fail ArgumentError, "invalid value for \"url\", must conform to the pattern #{pattern}."
       end
diff --git a/lib/lob/models/letter.rb b/lib/lob/models/letter.rb
index 1213533..2343ad5 100755
--- a/lib/lob/models/letter.rb
+++ b/lib/lob/models/letter.rb
@@ -67,7 +67,7 @@ class Letter
     # The tracking number, if applicable, will appear here when it becomes available. Dummy tracking numbers are not created in test mode.
     attr_accessor :tracking_number
 
-    # Tracking events are not populated for registered or regular (no extra service) letters.
+    # An array of tracking_event objects ordered by ascending `time`. Will not be populated for letters created in test mode.
     attr_accessor :tracking_events
 
     # Specifies the address the return envelope will be sent back to. This is an optional argument that is available if an account is signed up for the return envelope tracking beta, and has `return_envelope`, and `perforated_page` fields populated in the API request.
@@ -401,7 +401,7 @@ def list_invalid_properties
         invalid_properties.push("invalid value for \"template_version_id\", must conform to the pattern #{pattern}.")
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !@url.nil? && @url !~ pattern
         invalid_properties.push("invalid value for \"url\", must conform to the pattern #{pattern}.")
       end
@@ -414,10 +414,6 @@ def list_invalid_properties
         invalid_properties.push('invalid value for "description", the character length must be smaller than or equal to 255.')
       end
 
-      if !@tracking_events.nil? && @tracking_events.length > 0
-        invalid_properties.push('invalid value for "tracking_events", number of items must be less than or equal to 0.')
-      end
-
       invalid_properties
     end
 
@@ -434,12 +430,11 @@ def valid?
       return false if @id !~ Regexp.new(/^ltr_[a-zA-Z0-9]+$/)
       return false if !@template_id.nil? && @template_id !~ Regexp.new(/^tmpl_[a-zA-Z0-9]+$/)
       return false if !@template_version_id.nil? && @template_version_id !~ Regexp.new(/^vrsn_[a-zA-Z0-9]+$/)
-      return false if !@url.nil? && @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      return false if !@url.nil? && @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       return false if @object.nil?
       object_validator = EnumAttributeValidator.new('String', ["letter"])
       return false unless object_validator.valid?(@object)
       return false if !@description.nil? && @description.to_s.length > 255
-      return false if !@tracking_events.nil? && @tracking_events.length > 0
       address_placement_validator = EnumAttributeValidator.new('String', ["top_first_page", "insert_blank_page", "bottom_first_page_center", "bottom_first_page"])
       return false unless address_placement_validator.valid?(@address_placement)
       true
@@ -495,7 +490,7 @@ def template_version_id=(template_version_id)
     # Custom attribute writer method with validation
     # @param [Object] url Value to be assigned
     def url=(url)
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !url.nil? && url !~ pattern
         fail ArgumentError, "invalid value for \"url\", must conform to the pattern #{pattern}."
       end
@@ -535,16 +530,6 @@ def merge_variables=(merge_variables)
       @merge_variables = merge_variables
     end
 
-    # Custom attribute writer method with validation
-    # @param [Object] tracking_events Value to be assigned
-    def tracking_events=(tracking_events)
-      if !tracking_events.nil? && tracking_events.length > 0
-        fail ArgumentError, 'invalid value for "tracking_events", number of items must be less than or equal to 0.'
-      end
-
-      @tracking_events = tracking_events
-    end
-
     # Custom attribute writer method checking allowed values (enum).
     # @param [Object] address_placement Object to be assigned
     def address_placement=(address_placement)
diff --git a/lib/lob/models/postcard.rb b/lib/lob/models/postcard.rb
index 4689978..324bbea 100755
--- a/lib/lob/models/postcard.rb
+++ b/lib/lob/models/postcard.rb
@@ -334,7 +334,7 @@ def list_invalid_properties
         invalid_properties.push('invalid value for "url", url cannot be nil.')
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if @url !~ pattern
         invalid_properties.push("invalid value for \"url\", must conform to the pattern #{pattern}.")
       end
@@ -360,7 +360,7 @@ def valid?
       object_validator = EnumAttributeValidator.new('String', ["postcard"])
       return false unless object_validator.valid?(@object)
       return false if @url.nil?
-      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       return false if !@description.nil? && @description.to_s.length > 255
       true
     end
@@ -451,7 +451,7 @@ def url=(url)
         fail ArgumentError, 'url cannot be nil'
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if url !~ pattern
         fail ArgumentError, "invalid value for \"url\", must conform to the pattern #{pattern}."
       end
diff --git a/lib/lob/models/self_mailer.rb b/lib/lob/models/self_mailer.rb
index 357c8d4..4a622b7 100755
--- a/lib/lob/models/self_mailer.rb
+++ b/lib/lob/models/self_mailer.rb
@@ -53,7 +53,7 @@ class SelfMailer
     # Value is resource type.
     attr_accessor :object
 
-    # An array of tracking events ordered by ascending `time`. Not populated in test mode.
+    # An array of certified tracking events ordered by ascending `time`. Not populated in test mode.
     attr_accessor :tracking_events
 
     # A [signed link](#section/Asset-URLs) served over HTTPS. The link returned will expire in 30 days to prevent mis-sharing. Each time a GET request is initiated, a new signed URL will be generated.
@@ -128,7 +128,7 @@ def self.openapi_types
         :'outside_template_version_id' => :'String',
         :'inside_template_version_id' => :'String',
         :'object' => :'String',
-        :'tracking_events' => :'Array<TrackingEventNormal>',
+        :'tracking_events' => :'Array<TrackingEventCertified>',
         :'url' => :'String',
         :'use_type' => :'SfmUseType'
       }
@@ -284,7 +284,7 @@ def list_invalid_properties
         invalid_properties.push('invalid value for "url", url cannot be nil.')
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if @url !~ pattern
         invalid_properties.push("invalid value for \"url\", must conform to the pattern #{pattern}.")
       end
@@ -305,7 +305,7 @@ def valid?
       object_validator = EnumAttributeValidator.new('String', ["self_mailer"])
       return false unless object_validator.valid?(@object)
       return false if @url.nil?
-      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       true
     end
 
@@ -407,7 +407,7 @@ def url=(url)
         fail ArgumentError, 'url cannot be nil'
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if url !~ pattern
         fail ArgumentError, "invalid value for \"url\", must conform to the pattern #{pattern}."
       end
diff --git a/lib/lob/models/snap_pack.rb b/lib/lob/models/snap_pack.rb
index c13aef5..76b6ac2 100755
--- a/lib/lob/models/snap_pack.rb
+++ b/lib/lob/models/snap_pack.rb
@@ -1,7 +1,7 @@
 =begin
 #Lob
 
-#The Lob API is organized around REST. Our API is designed to have predictable, resource-oriented URLs and uses HTTP response codes to indicate any API errors. <p> Looking for our [previous documentation](https://lob.github.io/legacy-docs/)? 
+#The Lob API is organized around REST. Our API is designed to have predictable, resource-oriented URLs and uses HTTP response codes to indicate any API errors. <p> Looking for our [previous documentation](https://lob.github.io/legacy-docs/)?
 
 The version of the OpenAPI document: 1.3.0
 Contact: lob-openapi@lob.com
@@ -24,7 +24,7 @@ class SnapPack
 
     attr_accessor :size
 
-    # An internal description that identifies this resource. Must be no longer than 255 characters. 
+    # An internal description that identifies this resource. Must be no longer than 255 characters.
     attr_accessor :description
 
     # Use metadata to store custom information for tagging and labeling back to your internal systems. Must be an object with up to 20 key-value pairs. Keys must be at most 40 characters and values must be at most 500 characters. Neither can contain the characters `\"` and `\\`. i.e. '{\"customer_id\" : \"NEWYORK2015\"}' Nested objects are not supported.  See [Metadata](#section/Metadata) for more information.
@@ -284,7 +284,7 @@ def list_invalid_properties
         invalid_properties.push('invalid value for "url", url cannot be nil.')
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if @url !~ pattern
         invalid_properties.push("invalid value for \"url\", must conform to the pattern #{pattern}.")
       end
@@ -305,7 +305,7 @@ def valid?
       object_validator = EnumAttributeValidator.new('String', ["snap_pack"])
       return false unless object_validator.valid?(@object)
       return false if @url.nil?
-      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      return false if @url !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       true
     end
 
@@ -407,7 +407,7 @@ def url=(url)
         fail ArgumentError, 'url cannot be nil'
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if url !~ pattern
         fail ArgumentError, "invalid value for \"url\", must conform to the pattern #{pattern}."
       end
diff --git a/lib/lob/models/thumbnail.rb b/lib/lob/models/thumbnail.rb
index d701cbc..b848a03 100755
--- a/lib/lob/models/thumbnail.rb
+++ b/lib/lob/models/thumbnail.rb
@@ -85,17 +85,17 @@ def initialize(attributes = {})
     # @return Array for valid properties with the reasons
     def list_invalid_properties
       invalid_properties = Array.new
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !@small.nil? && @small !~ pattern
         invalid_properties.push("invalid value for \"small\", must conform to the pattern #{pattern}.")
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !@medium.nil? && @medium !~ pattern
         invalid_properties.push("invalid value for \"medium\", must conform to the pattern #{pattern}.")
       end
 
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !@large.nil? && @large !~ pattern
         invalid_properties.push("invalid value for \"large\", must conform to the pattern #{pattern}.")
       end
@@ -106,16 +106,16 @@ def list_invalid_properties
     # Check to see if the all the properties in the model are valid
     # @return true if the model is valid
     def valid?
-      return false if !@small.nil? && @small !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
-      return false if !@medium.nil? && @medium !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
-      return false if !@large.nil? && @large !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      return false if !@small.nil? && @small !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
+      return false if !@medium.nil? && @medium !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
+      return false if !@large.nil? && @large !~ Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       true
     end
 
     # Custom attribute writer method with validation
     # @param [Object] small Value to be assigned
     def small=(small)
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !small.nil? && small !~ pattern
         fail ArgumentError, "invalid value for \"small\", must conform to the pattern #{pattern}."
       end
@@ -126,7 +126,7 @@ def small=(small)
     # Custom attribute writer method with validation
     # @param [Object] medium Value to be assigned
     def medium=(medium)
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !medium.nil? && medium !~ pattern
         fail ArgumentError, "invalid value for \"medium\", must conform to the pattern #{pattern}."
       end
@@ -137,7 +137,7 @@ def medium=(medium)
     # Custom attribute writer method with validation
     # @param [Object] large Value to be assigned
     def large=(large)
-      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9-_]+/)
+      pattern = Regexp.new(/^https:\/\/lob-assets.com\/(letters|postcards|bank-accounts|checks|self-mailers|cards)\/[a-z]{3,4}_[a-z0-9]{15,16}(_signature)?(\.pdf|_thumb_[a-z]+_[0-9]+\.png|\.png)\?(version=[a-z0-9]*&)expires=[0-9]{10}&signature=[a-zA-Z0-9_-]+/)
       if !large.nil? && large !~ pattern
         fail ArgumentError, "invalid value for \"large\", must conform to the pattern #{pattern}."
       end