You use the product_class field to add product class to your requests. It ca be for physical goods or shipping and other charges.

Physical Goods

To specify a good as a physical good, you can add product_class=P, as follows:

{
"product_class": "P",
"quantity": 2,
"description": "Oak smoked kippers (1kg)",
"amount": "29.00",
"custom_id": "51315A00-DC44-408E-A575-8CE42A32AE1B",
"import_address": {
"country_code": "FR"
},

Shipping and Other Charges

Details about how to add the Product Class for shipping and other charges is provided in the Shipping and Other Charges topic.