Custom supplies are simply another attribute within the product feed. These can be used in your shopping campaign , which allows you to identify, group, filter and structure products in order to apply your product listing ad strategies. For example you may want to use a different bid strategy for some items. Examples, of custom labels Brand, Release year, Best sellers, Margin, Season, special shipping, Attributes of the item including colour, size etc. Using custom labels allows advertiser to make bid changes and adjustments quickly and effectively.