The CMMG Banshee 100 MK57 5.7x28 Complete Upper is a M4 style upper featuring CMMG's patented Radial Delayed Blowback operating system. It features a durable and reliable 8-inch steel barrel chambered in 5.7x28mm with a 1:9 twist rate and 1/2"x28 threaded barrel for optimal performance and functionality. It features a 7075-T6 aluminum construction making it strong and fatigue resistant. The CMMG upper boasts a type III hard coat anodized finish to ensure it can withstand the most severe abuse and provide maximum corrosion resistance. The 5.7x28mm upper features a M4 feed ramp to promote consistent and reliable feeding. This CMMG upper offers a RML7 M-LOK handguard for the attachment of a wide variety of tactical accessories. In addition, to the M-LOK the upper provides a Mil-Spec charging handle, and A2 compensator. The Banshee 100 5.7x28mm comes with a complete bolt carrier group and a lifetime quality guarantee. If you are looking to build your next AR platform rifle in 5.7x28mm and looking for exceptional repeatability and incredible durability, the CMMG Banshee 100 MK57 is a great option.Features: 5.7x28mm 8-inch steel barrel 7075-T6 aluminum 1/2" x 28 threaded muzzle M4-style feed ramp 1:9 RH twist rate Type III hard coat anodize Mil-Spec charging handle RML7 M-LOK handguardA leading manufacturer of AR-15 rifles, kits, and accessories, CMMG Inc. was established in 2002. Constantly pushing the edge, CMMG strives to develop and improve bringing you a product lineup that is second to none.