Got a pile of Colt AR 9mm magazines that you'd like to feed through your KE Arms KE-15 receiver? You're in luck. The company now has this specially developed 9mm adapter designed to convert the KE Arms KP-15 and KE-15 lower receivers to feed from Colt-style AR 9mm magazines. Not only does this mean you can run those Colt mags you've got, you can also run any Colt/RRA 9mm upper receivers, too! Each KE Arms 9mm Adapter uses the standard bolt catch that holds open after the last round is fired. To install this adapter, you'll need to remove the bolt catch, insert the adapter and then reinstall the bolt catch. This adapter will not function on standard aluminum lower receivers.