Just add your AR15 Lower Receiver/Stock Assembly to this 7.62 X 39mm Caliber Windham Weaponry Flattop Upper Kit and you’re ready for the range. The complete Upper Receiver Assembly includes a 16″ M4 profile Barrel in 7.62 X 39mm complete with Handguards, a Mil Std 1913 Railed Front Sight Base/Gas Block with Sling Swivel,  a 7.62 x 39mm Bolt & Bolt Carrier, and 30 Round 7.62 X 39mm Magazine. The Barrel is 4150 Chrome Moly Vanadium 11595E Steel, Chrome Lined in Bore and Chamber, rifled 1 turn in 9.5 inches – right hand twist – with 4 lands & grooves. The muzzle is fitted with an A2 Birdcage Type Flash Hider (threaded 5/8 x 24).