<p>Upgrade your AR platform .308 with the PWS MK220 Mod 1 complete upper receiver assembly. The MK220 Mod 1 upper features a gas piston operating system design with an adjustable gas block, a KeyMod handguard and free-floated barrel. The PWS Key-Mod hand guard allows you to add Key-Mod accessories or Picatinny rail sections only where you need them. This reduces the width profile and weight of your rifle streamlining your AR10 platform! Take your modern musket to state of the art sporting rifle with the PWS MK220 Mod 1 upper receiver. Specifications and Features Primary Weapon Systems MK220 Mod 1 M220RC1B Complete Upper Receiver 308 Winchester accepts 7.62x51mm NATO 20″ Stainless Steel Heavy Profile Barrel Isonite QPQ Treated Barrel Button Rifled with a 1:10 Twist FSC 30 Muzzle Device PWS Mil-Spec 7075 Aluminum Upper Long Stroke Gas Piston 4 Position Adjustable Gas Block PWS Nickel-Teflon Coated Enhanced BCG PWS 6061 Aluminum Free Float Handguard Full Length Picatinny Top Rail with Key-Mod Weight 7 Pounds Mil-Spec Type III Hardcoat Anodized Finish Black</p>