This class identifies an individual saleable or dispensable unit of medication, and is used to convey information about the actual drug produced, dispensed, or administered. Note that the Id property (commonly known as a serial number) would be used to identify the saleable unit. It is widely anticipated that saleable units will have such Ids in the future, but it is currently not common practice. "A product instance is (a) an individual product instance, i.e., an individually identified thing with a serial number; (b) a product lot, i.e., a set of things of the same kind (e.g., 1000 for expressing a number of tablets) or an amorphous mass (e.g., 100 L of a liquid raw material), or (c) any subset, member, or portion of a product lot. The distinction between an individual thing and a lot is made in the quantity attribute, which is set to 1 (one) for individual items, or any number e.g., 1000 or amount 100 L for sets of things or amorphous masses respectively." - HL7 Version 3.