These floor plates add two additional rounds to factory Glock magazines in 9mm, and one additional round in magazines in .40S&W. The floor plates provide an additional gripping surface for more positive control of the pistol. No permanent modification required. Constructed black, injected-molded polymer. DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.