O-Rings
FSC 5331: O-Rings
Federal Supply Class (FSC) 5331 covers O-rings, the round-section elastomeric seals used to seal static and dynamic joints. The catalog includes O-rings built to AS568, MIL-SPEC, and industry standards.
O-rings seal connections in hydraulic, pneumatic, fuel, and fluid systems by compressing in a groove. They are among the most widely used sealing elements in machinery.
Common materials include nitrile (Buna-N), fluorocarbon (Viton), silicone, EPDM, and PTFE, selected for fluid compatibility and temperature range. Sizes follow standard dash-number series for repeatable replacement.