Just thought I'd add my experience to this. I got the copper/crinkle black kit a few weeks back, and the o rings were absolutely ridiculous on it, 4 or 5 on-offs with the cap and the rings just completely shit themselves. As for the afc cap, forget it, completely seized, couldn't move it. Got it off eventually, chenged it, lubed, put back on. Did the same thing. All rings lubed generously. Two lots of spares sent to me, no dice. Now returned the kit and been sent the SS one. Perfect. No problems whatsoever, beautiful tolerance on all rings. I think there must either be a problem with some o rings, or the fact they're binding up on the copper. Or both. Either way the SS one is fine.