-Machined to MIL spec from 7075 T6 forgings -Top MIL-Std 1913 Rail -Hardcoat Anodized per MIL-A-8625F, Type III, Class 2 -For Use with M4 Barrel extensions -Assembled Upper Receivers come with ejection port cover and forward assist installed -Made in America on American-made machines -Weight: .8.3oz