I was helping build a pistol for a bud and when he finally got me his lower, it was 9mm dedicated so this was never installed, NIB, fits any std AR15 lower magwell and adapts to accept 9mm Glock magazines. Pics from their website. "This Mag-well Conversion block quickly and easily gives your current Mil-Spec AR-15 Lower receiver the ability to use 9mm Glock and Glock Compatible Magazines. " and I know what I paid there, over $110 incl shipping so, save the change and get to meet an outstanding ODT enthusiast.
