GuntecAR15 9MM Dedicated Stripped Billet Upper Receiver – Flat Dark Earth Cerakote Flat Dark Earth Finish 9MM Cal Ejection Port Opening Measurement : 0.61″ Width x 2.30″ Length T6 6061 Billet  1913 Picatinny Rail Flat Top Smooth “Slab Side” Design MIL-A-8625 TYPE III Anodizing Will Match Up With Any Brand 9mm Lower Receiver Such As New Frontier, Palmetto State Armory, & Circle Quarter 10 US Made in Scottsdale, Arizona Mirror