Yes. When I bought an EX88 new all those years ago, it had a plastic tube as a piston sleeve, sealed where it sits on the inside of the piston. When I stripped the rifle to correct a power issue (ott) I found the end of the tube had detached from the sides .. very neatly. I mentioned this to Air Arms at a fair (Midland??) and they sent me a new sleeve tube.
Cheers, Phil