O-ring Face Seal (OFS) fittings were designed to eliminate leakage problems and still handle the greater pressure of today's hydraulic systems. They are dimensionally standardlized by SAE under J1453. It utilizes a Buna-N, 90 durometer O-ring that seats into a groove on the body and compresses against a flat face sleeve on the end of a tube. The sleeve also prevents twisting of the tube and supports it during the assembly process. When the sleeve comes in contact with the body and starts compressing the O-ring, a noticeable rise is required to complete the assembly. This deters over-torque abuse and avoids distortion making a leak-proof, full flow connection. The OFS design can be used multiple times by just simply replacing the O-ring.