I hope I'm not repeating old info here. I don't think I've seen a thread on these yet. Just Visited Downrange.TV and saw an interview with a GLOCK rep at SHOT show introducing the GEN 4 GLOCK 21. It has the new recoil spring, mag release, and grip texture. He said the frame WITHOUT backstrap was the same as the already available SF version. The first backstrap makes it the size of the old G21, and then they have a backstrap bigger than that (for the one human being who may have hands that big). I guessed a long time ago that the G21/G20 frames were already as small as they were going to get. Too bad I was right... They also introduced a new backstrap that had a beavertail, but he did not say whether it would have the same GLOCK hump in it or not.