As differentiated by material in accordance with ships parts control center activity hx quality control,manufacturing and testing specifications reference number differentiating characteristics

A circular shaped item with an aperture manufactured to predetermined dimensions and designed for use as a seal in stuffing boxes, packing nuts, and the like. It may be (1) any nonmetallic molded or formed ring (except solid (without joint) rings having a square or rectangular cross section); or (2) any shredded metal or metal foil type metallic or semimetallic rings. Excludes:felt items but includes multimaterial items in which one of the materials is felt. For solid (without joints) nonmetallic items with a square or rectangular cross section, see washer (as modified) and gasket. For rubber items specifically designed for weather-proofing doors, windows, chests, and the like see seal, nonmetallic angle; seal, nonmetallic channel; and seal, nonmetallic, special shaped section. For circular (with aperature) nonmetallic items with a solid round cross-section see o-ring. Excludes:cup, compression; gasket; washer (as modified); and felt, mechanical, preformed.