This upper combines a 6061-T6 billet receiver with tight milspec tolerances and a compact 5in M-LOK handguard featuring an integrated handstop for confident handling. The 5in 4150 CMV barrel with a 1:7 twist, chambered in .300 AAC Blackout, is optimized for versatile loads in tight quarters. A 5/8x24 aluminum flash can, .750 steel gas block, steel barrel nut, and micro gas system ensure smooth, reliable cycling. Finished with an MPI-tested nitride BCG, forged extended-latch charging handle, and full milspec forward assist and ejection port hardware, this upper is compact, clean, and built to hit hard. Specifications for ABC RIFLE COMPANY AR-15 .300 AAC Blackout Micro Pistol 5in Barrel Custom 5in Top Cut Custom M-LOK Handguard Complete Upper Receiver w/BCG And Charging Handle: Manufacturer: ABC RIFLE COMPANY Caliber: .300 AAC Blackout Barrel Length: 5 in Barrel Twist Rate: 1-8 Threads per Inch: 5/8x24 Muzzle Device: Muzzle Diverter Flash Can Handguard Length: 5 in Gun Rail: M-LOK Gun Type: Rifle Gun Make: AR Platform Gun Model: AR-15 Gas Block Journal Size-Length: .750 in Bolt Carrier Group Included: MIL-SPEC Charging Handle Included: MIL-SPEC Package Contents: ABC RIFLE COMPANY AR-15 .300 AAC Blackout Micro Pistol 5in Barrel Custom 5in Top Cut Custom M-LOK Handguard Complete Upper Receiver w/BCG And Charging Handle What firearm models does the manufacturer say ABC RIFLE COMPANY AR-15 .300 AAC Blackout Micro Pistol 5in Barrel Custom 5in Top Cut Custom M-LOK Handguard Complete Upper Receiver w/BCG And Charging Handle is compatible with? The manufacturer suggests that ABC RIFLE COMPANY AR-15 .300 AAC Blackout Micro Pistol 5in Barrel Custom 5in Top Cut Custom M-LOK Handguard Complete Upper Receiver w/BCG And Charging Handle is compatible with AR-15