Lonex Hollow O-rings (5 pack)

Amazing O-Rings, I have put them in a couple different piston heads from generic ones that come in chinese guns, to better metal ones and all of them gave perfect compression.

The offset flash at 45 degrees from the injection is a genius idea, and works exactly as expected.

They're a little expensive but frankly, it's worth it. The perfect compression you get from these easily offsets the ~$2 you pay for each one. I'll be getting more to put them in all of my guns from now on.