A SKU (stock keeping unit) represents a purchasable instance of a product on a site. Customers do not actually purchase products, they purchase SKUs. A product can have several different SKUs associated with it, representing varieties, sizes, and colors. For example, the product Hoodie Sundress, which is available in two different colors and five sizes, has ten associated SKUs, one for each size/color combination. SKUs have no child assets.

Usually, a SKU represents a single item, such as “blue shirt in size medium.” A configurable SKU represents something that is sold as a single item but has variable components, such as a computer system or a bicycle.