Converting your standard mil spec AR lower to a 9mm lower is easy with the 9mm conversion block. Insert the conversion block into the magazine well of your standard AR lower, and combined with most 9mm AR uppers you have a pistol caliber carbine. The trigger style magazine release makes removing the magazine with one hand easy. Features : Fits Glock 19/17 Magazine Aircraft Grade 6061 Aluminum Black GLOCK is a registered trademark of GLOCK Inc. 3CR Tactical is not affiliated with, endorsed by, or sponsored by GLOCK Inc. Any reference to GLOCK products is for identification and compatibility purposes only.