The product size is the size of the product.
Content
The size is not a mandatory product field. However, the field is recommended because it is commonly used in product sets and personalizations.
Go to Products
Click on the product and look at the product field Size
Is the field not filled in? Add the field to the implementation of the product feed
Implementation
The product field can be implemented manually with:
https://squeezely.atlassian.net/wiki/pages/resumedraft.action?draftId=1358856250