The PROLUBE 3-Jaw Hydraulic Couplers are engineered to be a durable and leak-proof connection with grease fittings to hand-operated Grease Guns. These couplers provide a quick connection on a 1/8" NPT thread while withstanding high pressures within its hardened body. The 3 fully hardened spring steel jaws ensure that the coupler securely attaches to the grease fitting providing a leak-proof seal. The hexagonal nut allows easy tightening, connecting, and disconnecting of the coupler from the grease fittings. This hydraulic coupler features a spring-loaded ball check valve that helps retain pressure.