This is a very handy coupler and it works great. the jaws retract to clamp on the Zerk and tighten up as they move forward in the housing. So when you start to pressurize the grease, these clamps just get tighter.

This grease pump coupler is a must-have for anyone using a grease gun. I recently had to grease a Zerk fitting on a tractor, and the gun's nozzle was stuck on so tightly that I had to pry it off using a crowbar. The tool detached easily from the same fitting, essential for greasing things.

This has got to be one of the handiest pieces of maintenance equipment ever invented. It solves the problem of trying to hold the grease gun nozzle on the fitting with one hand and operating the gun with the other while most of the grease oozes out of instead of going into the fitting. Just slip this coupler on the fitting and use both hands on the gun, grease goes into the fitting, no muss no fuss.

The grease pump coupler is easy to attach and so far has been 100% reliable for making a good connection with the grease fittings.

When I ran across this product, read the reviews, and did the research, it looked like a good fit. I have nothing negative to say about this product. It works well, is easy to use, and make greasing hub and wet bolts on my fifth wheel RV very easy.