Caliber: 9mm Luger (1:10). AR9 lower receivers with last-round bolt hold open compatible with 9mm service pistol magazines for Glock, Beretta, and Wilson Combat EDC X9. Accepts standard AR accessories. Integral trigger guard, flared magwell. Closed-bolt blowback operating system. Match-grade 8”, 16” button-rifled 1:10 twist barrels. Add $360 for Combat-Tuff finish. Introduced 2016.