The Taylor Freelance +8 magazine for the Glock 9mm Luger/ 40 S&W pistol is constructed of black Delrin. This magazine extension will increase the capacity of your factory magazine by 10 rounds in 9mm and 8 rounds in 40 S&W. The length of the magazine with the extension will not exceed the IPSC Open Class 170mm length rule when used on Glock 17 or 22 magazines. The extension works with the stock magazine follower and includes a custom length Wolff extra power spring for reliable operation. 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.