Has anyone seen these or tried them out? I just saw an ad for these is shotgun news magazine. It's a pretty versatile idea because you can get a different caliber upper than your glock. I don't think I would do it but I think it's pretty neat anyways. Also available for 1911 pistols. (I tried to attach a pic not sure if it will work.) From www.mechtechsys.com : Glock upper'BASIC UNIT' It consists of a 16+" barrel, internal slide, recoil spring, cocking handle and what you see externally. The basic unit is NOT a firearm and needs no special licensing to purchase! What do you need? You need a Glock or 1911 pistol. What do you need to do? Field strip your pistol. This will separate the 'top end' assembly from the frame or 'lower'. Now you slide the pistol lower into the Upper 'BASIC UNIT'