diff --git a/lib/checkout_sdk/payments/payments.rb b/lib/checkout_sdk/payments/payments.rb
index ef14016..7a9e39e 100644
--- a/lib/checkout_sdk/payments/payments.rb
+++ b/lib/checkout_sdk/payments/payments.rb
@@ -8,6 +8,8 @@
 require 'checkout_sdk/payments/user_action'
 require 'checkout_sdk/payments/three_ds_request'
 require 'checkout_sdk/payments/product_type'
+require 'checkout_sdk/payments/product_item_type'
+require 'checkout_sdk/payments/product_sub_type'
 require 'checkout_sdk/payments/payout_billing_descriptor'
 require 'checkout_sdk/payments/shipping_details'
 require 'checkout_sdk/payments/payer'
diff --git a/lib/checkout_sdk/payments/product.rb b/lib/checkout_sdk/payments/product.rb
index 03215ae..4c13b06 100644
--- a/lib/checkout_sdk/payments/product.rb
+++ b/lib/checkout_sdk/payments/product.rb
@@ -3,9 +3,13 @@
 module CheckoutSdk
   module Payments
     # @!attribute type
-    #   @return [String]
+    #   The item type. For example, +physical+ or +digital+.
+    #   [Optional]
+    #   @return [String, nil] {ProductItemType}
     # @!attribute sub_type
-    #   @return [String] {ProductSubType}
+    #   The digital item type. Required if +type+ is set to +digital+.
+    #   [Optional]
+    #   @return [String, nil] {ProductSubType}
     # @!attribute name
     #   @return [String]
     # @!attribute quantity
diff --git a/lib/checkout_sdk/payments/product_item_type.rb b/lib/checkout_sdk/payments/product_item_type.rb
new file mode 100644
index 0000000..9f3f0c4
--- /dev/null
+++ b/lib/checkout_sdk/payments/product_item_type.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module CheckoutSdk
+  module Payments
+    module ProductItemType
+      DIGITAL = 'digital'
+      DISCOUNT = 'discount'
+      PHYSICAL = 'physical'
+    end
+  end
+end