Please refer to DLA letter of August 8th 2019,  Proposed Cataloging Data Change (PCDC) 0018, Addition of New Units of Measure Parts Per Million and Percent Weight and Unit of Issue Sleeve (Cataloging/Supply/Contract Administration). This is the definitive listing of all DOD approved unit of issues.

         The document describes a  Lot as “A collection of associated or miscellaneous articles sold as one unit”.   Similar units of issue are 'kits" or "sets" and are defined in detail in the document. 

IT would be up to the suppliers description or the contracting officer’s judgment as to the appropriateness of the use of each term.  You can find the document by google  searching for the above description.