To who it may concern!!! Can this work on a Glock Model 21 45 Caliber before the generation 3, 4, and, 5? Please let me know when y'all get a chance. — 3 Answers

It's designed for the Gen 3 and above, but there is another G21 it won't fit. When Glock came out with the 21SF, they made two versions of the lower. One is the standard version which is exactly like the G21 non SF (except for the Slim part) and they made the Military version. The Military version has the full picatinny rail on the lower. It will absolutely NOT fit that pistol. I know because I have the military one and after 5 months of going back and forth with the distributor, I finally sent him a picture of my pistol and that's the cause of it. I ended returning the CAA for one that fits the G30.

The Glock Model 21 45 Caliber with out any printing on the frame. I called Glock Inc, and, they looked up my serial number for it!!! It's a Generation 3!!!