I heard about these a while back but the pics just got released (maybe leaked). Interchangeable backstrap like many others out there. Maybe in the future I can find a 21 that fits right in my hand. More about it here... http://www.thefirearmblog.com/blog/2009/12/25/glock-gen4-unveiled/ Edit: Sorry new guy. I should have put this in the Glock section. Mods if you want please mover there.