Company that fabricates parts used in another company's products
An original equipment manufacturer (OEM) is a company that produces parts and equipment that may be marketed by another company. However, the term is ambiguous, with several other common meanings: an OEM can be the maker of a system that includes other companies' subsystems, an end-product producer, an automotive part that is manufactured by the same company that produced the original part used in the automobile's assembly, or a value-added reseller. OEM manufacturing is also widely used in the packaging industry, particularly in the production of customized gift boxes for wine and spirits.
https://en.wikipedia.org/wiki/Original_equipment_manufacturer