The product, generic product, represents the ingredient, the pivotal element used in both purchasing and production.
Standard inventories are counted in generic products expressed in stocking units. (There is also a multi-unit inventory, which counts on delivery units (GU, DU,PU).
Recipes are based on generic product quantities expressed in production units (PU).
Lastly, call-off products are used in call for tender, using the product's unit of negotiation (UN) to express requirements to the various candidates.
Note that the call product is an overlay of the generic product (adding information such as volume).