Wabbit, some of the cartel boyz cases use the oversized retention ring w/plastic shim which will likely cause you some heartburn attempting a crystal change. You might get lucky and be able to get everything pressed back together, but if not PM me for options. I have installed gen tubes in these cases and it's just a matter of removing the old tube, running a tap through to clean threads, slightly countersink the tube hole in the case, and thread the new tube in with blue Loc-Tite...