The Black Diamond Adjustable Hydraulic Coupler is designed for use with hand-operated grease guns, providing a secure connection with an adjustable cap for an easy fit on the grease fitting. Fully hardened spring steel jaws and a hardened coupler body help it withstand high pressure without deformation. The 4-jaw construction with a ball check supports a consistent seal during greasing. Threaded 1/8" NPT with a 6,000 psi working pressure for dependable performance.