NLX556 AR15 Upper Receiver Every NLX556 AR15 upper starts with a quality forging in 7075 t6 Aluminum. Our team at Next Level Armament then machines these aerospace grade materials into a precise and smooth upper receivers. Once tumbled and inspected, each receiver is hard coat anodized to mil-spec thickness to ensure you receive a durable and reliable product. Small things make a difference, like our unique scallop down the top of the receiver. This feature reduces weight, adds some flair to your rifle, and matches our NLX556 MLOK Handguards. We open the ports on all of the uppers during our finishing process to accommodate larger calibers , so whether you're building anything between .223 and .450 Bushmaster, we have you covered. Combined with the NLX556 AR15 Lower, your rifle will have quality and durability at an affordable price.