For 3PL items, the orderItemGroup is simpler because there is no decoration information needed. designData is omitted and the sku field is provided with a value corresponding to one of the 3PL SKUs registered in the store.

Below is an example of a 3PL orderItemGroup.

{
  "declaredValue": 12,
  "id": "47b8274d-ae30-4564-a6f8-66bc4504829a",
  "sku": "7352583123",
  "quantity": 8
}

If you have registered values for Vendor SKU on the 3PL items in the store, the Vendor SKU can be used instead on the orderItemGroup. 

{
  "declaredValue": 12,
  "id": "47b8274d-ae30-4564-a6f8-66bc4504829a",
  "vendorSKU": "QAR-3431",
  "quantity": 8
}