There are a few choices out there now. POF-USA DS Arms Lauer Weaponry Bushmaster/Quality Parts Z-M Weapons There may be more. Is this the wave of the future? I personally do not like the gas impingement system of the M16/AR15 for two reasons: (1) dumping ash into the chamber area makes cleaning a PITA. It's a little easier on the MAS 49/56, because the parts are large and crude, and the receiver has no nooks and crannies. But on the AR15, it takes 4 times as long to clean properly. (2) Buffer tubes suck. They look hokey. They sound funny during recoil. Because they don't fold, the most compact configuration is larger than it needs to be. If you can think of any more vendors or designs for piston ARs, please post them. I would like to do a comparison of all the entries.