prostock is like a trilogy its pressed on ( i believe ) but the super stock just screws off like any other marker, thats why trinity made the trinity trilogy/prostock clamping feed neck that slides over the top
dont know if i can plug sites on here but Ansgear.com are doing them for about £100 for a superstock + Postage + tax... which is a lot cheaper than anywhere in the Uk like justpaintball still has them for £600....
but buying from abroad kills the Uk Paintball Econimy