This attribute describes the material or fabric of a product.
The attribute 'material' is required for items in an item group with different variants of material. For items whose material is a significant attribute it is recommended.
If you have items with different variants of material you have to submit every variant as a separate item. In addition you have to use the item group id. If you want to set more than one material for an item you have to specify a primary material. Then you can add one or two secondary materials separated by a '/' (e.g. polyester/cotton/elastane).