Turn your Glock 22-round .40 into a 25! Shooters running .40 S&W Glocks in USPSA's "Open" Division contacted us about extending Glock's new 22-round magazine (about 160mm long) out to 170mm. The result is the "Supercap" -- a slick little +3 that is guaranteed to stay on the gun, no matter what. (Some of the cheapy +2's will pop off if dropped on a rock.) CNC'ed out of Delrin bar stock, there's no better option. (Delrin is a hard, machinable polymer that won't damage your expensive magazines.) If you want maximimum magazine capacity for a Glock .40, this is the way to go. Works with the stock magazine spring. -- Also works on Glock 17 or Glock 22-length magazines when using them in a subcompact pistol such as the Glock 26. -- Also works on 30-round 9mm Glock magazines (Glock name brand only, others, maybe, maybe not).