High-strength, aircraft aluminum base pad slides open to accept magazine body and locks into place. Removes in seconds for easy cleaning. Base pad increases capacity of 15 round, .40S&W magazines by three rounds and 9mm magazines by 4 rounds. Maintains 140mm USPSA rule and increases magazine to maximum levels for competition. Comes with extra-power, steel spring and installation instructions. Mfg: Dawson Precision SPECS: Aluminum, black. Steel mag spring. Fits small frame Glock 9mm & .40 S&W pistols.