I have a Nitro Piston sitting in my toolbox that I took out of my CFX. I replaced it with a Theoben gas ram after noticing that the velocity dropped from 930 fps to 650 fps in my .177 cal. CFX. If yours is a Nitro Piston made by Crosman, you could probably call up Crosman, ask to speak to one of the superiors there, and ask him to send you a replacement gas ram, but if I were you, I'd get the Theoben gas ram.