Short stroke gas piston system based around the Taiwanese T91 but made for American market as the A1 by Wolf Ammunition.

Used but in great shape. Maybe just a hair over 1k rounds through it. Never had a jam or issue and groups well. I sprayed the handguard with a durable green spray that matches the other furniture as well as added a pic rail section on the side for a light mount.

If you have any questions feel free to write me or research the system online, they are very interesting. Lots of aftermarket accessory options are available through T91 Tactical as well