The AR-9 lower is based off the V3.0 Super AR-15 Lower. It is designed to use Glock mags. Both the mag catch and ejector are 3D printed. The only non AR-15 part needed is the 3/32″ x 1″ roll pin for the mag catch. Keep in mind that this is the first release of the AR-9 lower, there may be bugs which still need to be worked out.