Item of supply means an item of production that is purchased, cataloged, and assigned a national stock number by the Government. The item of supply is determined by the requirements of each Government agency's supply system. The item of supply concept differentiates one item from another item in the Federal Catalog System. Each item of supply is expressed in and fixed by a national item identification number. An item of supply may be:

(a) A single item of production;

(b) Two or more items of production that are functionally interchangeable;

(c) A more precise quality controlled item than the regular item of production, or

(d) A modification of a regular item of production.

[46 FR 35644, July 10, 1981]