Modify your Glock™ magazines to lock into AR15 mag catches with the included trim guide, or use TorkMag 20rd G17 magazines that are pre-molded with an AR15 mag catch slot. In less than a minute, you can still switch back to 5.56mm without any permanent changes to your lower. Each kit ships with polymer magwell blocks mated to a steel fixed ejector, a mag-cutting guide, and a hex key for press fitting the magwell blocks in position.