The Adams Arms PZ model is the perfect platform for shooters who enjoy building and customizing their rifle. The PZ model includes our Picatinny Railed Gas Block with 3 adjustable settings, M4 furniture, and the KAK Blade Brace. The PZ is your Piston Driven foundation, ready to be customized to fit your needs. Specs- barrel contour- M4, M4 feed ramps, gas system length- carbine, short stroke piston operated, gas block diameter- 0.750", M4 handguards.