Pearce Grip's Plus Extension adds capacity to full metal-lined Glock magazines for Generation 4 sub-compact, mid-, and full-size Glock high capacity magazines. This magazine extension replaces the original floor plate and internal locking plate and adds two rounds to a 9mm, two rounds to a 40SW and 357SIG, and one round to a 45GAP magazine. This unit will not fit the 10mm or 45ACP models. It is made from high impact polymer and withstand drop tests at temperatures from -20 F to 350 F.