CMMG's Mk4 RCE .300 AAC Blackout Upper features a RKM14 free-floating KeyMod handguard for nearly unlimited customization options. 16.1" 416 stainless steel barrel with a medium taper and a bead-blasted finish. Muzzle boasts a removable SV brake attached with 5/8"-24 threading. Exceptionally durable forged 7075-T6 aluminum M4-type upper receiver. Includes the upper receiver, ejection port cover, forward assist, barrel subassembly, handguards with barrel nuts, charging handle and bolt carrier group. CMMG lifetime quality guarantee. Made in USA.