Special Features:

As568 called for two classes of tolerances for inside diameters. Class ii was for o-rings made of higher-shrinkage elastomers, such as fluorocarbon and fluorosilicone. Class i was for o-rings made of other elastomers; class ii permitted wider tolerances than class i; o-ring size: 264

Properties:

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.