The PROLUBE Professional 4-Jaw Hydraulic Coupler (43502) is also available in boxes of 54. These 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 while withstanding high pressures within its hardened body. The 4 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.