Faxon Firearms Modular Magazine Extensions are rigorously tested with and engineered. Machined from 6061 T6 aluminum with a type 2 anodize finish, the unique modularity of these extensions allows users to choose from a number of setups and finishes for their pistol. All Faxon Modular Magazine Extension Kits include assembly screws, while +5 and combo kits also include a +5 compatible spring. +2/3 kits are OEM spring compatible. When assembled, screws should be torqued to 12-15 in/lbs. 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.