The Wilson Combat AR-15 matching receiver set is hand selected to ensure a proper fit between upper and lower halves. This "better than mil-spec" set accepts all aftermarket and mil-spec internal parts."Multi" caliber marked. Not "T" Marked for a custom look.FeaturesGI style Upper and Lower machined from 7075-T6 Aluminum USA-sourced forgings.Closed Trigger GuardM4-style feedramps for flawless feeding.Will accept all mil-spec parts.Multi caliber Markings (forging stamp may vary)Anodized Black finish