Chambered in 5.56 NATO with 18.5-in. barrel, Geissele trigger, Magpul PRS or PRS2 stock (current model). Modular design on current production model for quick and easy caliber change. Designated Marksman Rifle. Model no. 90958. 5.56/18.5 in. 51T AAC flash hider. Prices shown are for 18.5-in./5.56mm model 90958.