I've always liked the 21, but until the SF, they were just to bulky for me. Skip forward to present day, and I've picked up a very nice Gen 4. Without the back strap installed, it fits even better than the SF did. I was initially a little disappointed as it trickled brass on the brim of my hat from the first round. Not a 21, that just doesn't happen! I guess this was a hit or miss issue with the Gen 4 21's, mine missed. I was about to just take the loss and be rid of it, but decided I needed to at least give it a chance. Rather than pay to ship it back to Glock, I decided to spend that money and replace a few parts. Now, a couple weeks later and a new Lone Wolf extractor, stainless single spring recoil rod, and .40 ejector from NDZ, she dumps brass 3' right and to the rear in a nice little pile. Function and accuracy are absolutely perfect. I know it's no longer technically stock, but I'd take this gun to war any day. Kudo's to Lone Wolf, their machined stainless extractor is wonderful, holding the brass nice and tight to the breech face. As to the Gen 4 .40 ejector, I don't know why it works so much better than the OEM designed .45 ejector, but it does and is more robust as well. And the recoil rod, personally, I think they should have never changed to the dual spring RSA. The recoil on the 21's was never that bad to start with. The extractor stopped the BTF, the recoil rod and spring, pushed the brass a little further from the gun, and the ejector finished the job by making the ejection very positive and uniform. I shot 6 rounds as fast as I could squeeze the trigger, and all the brass landed within a 6" circle. Made picking up my brass a piece of cake. I'm liking it so much now, I'm thinking about buying her a really nice holster, maybe a Tucker.