Lincoln Heavy duty grease coupler of 11/16" hex and features built-in ball-check that prevents leak. Coupler features 1/8" NPT male inlet adapter connection and operating pressure of 7500 psig. Size: 11/16 hex. Operating pressure: 7500 psi [max]. Connection: 1/8 NPT male inlet adapter. Small outside diameter permits easy contact with recessed fittings. Built-in ball-check prevents leak and lubricant backup. For all hydraulic type grease fittings. Lincoln Heavy Duty Grease Coupler features small outside diameter that permits easy contact with recessed fittings.