Tool-less Design. Slide opens and closes to remove base pad. Removes in a second to clean your high cap magazine. Meets 140mm rule for USPSA and increases capacity to the maximum. Gives you 19-20 rounds in .40 and 22-23 rounds in 9mm. CNC machined from aircraft aluminum. Comes with extra power mag spring and instructions on how to install. Use only with 9 mm and 40 S&W Glocks. Available in black and silver. Note: these basepads will not work with 10 round magazines or with magazines for compact or subcompact model Glocks.