The LockNLube Grease Coupler XL, just like the shorter original, is compatible with all grease guns and grease fittings. It does not leak once locked on and will not pop off under pressure. No hands are needed to align or hold the coupler in place while greasing. You have both hands free to operate your grease gun and know that the grease will go in, not on, your machine. Guaranteed. The XL is suited for all machines, but especially useful for U-Joints, Harvester Heads, shielded PTO shafts, and any fittings buried deep behind a shield. With almost 4" of reach, you can be confident that you'll reach your fittings and grease will go in, not on, your machine. When you want to release the coupler, simply depress the thumb lever, even at extreme pressures.