High Performance FKM O-Ring — Black, Brown, Green Color Options — Heat & Oil Resistant Seal An O-ring, also called a packing or toric joint, is a mechanical gasket shaped as a torus — a loop of elastomer with a round cross-section. It is designed to sit in a groove and be compressed during assembly between two or more parts, forming a seal at the interface. O-rings can be used in static applications as well as dynamic ones, where relative motion occurs between the parts and