An arbitrary alphanumeric unique ID, specified by the seller, which identifies each item. This will be used by the seller in the XSD file to refer to each item. Special characters in the sku needing encoding are: ':', '?', '#', '[', ']', '@', '!', '$', '&', "'", '(', ')', '*', '+', ',', ';', '=', as well as '%' itself. Other characters don't need to be encoded.
Market availability: Global