Daniel Defense 04-012-09001 Big Hole Flat Top Upper Receiver with Feed RampsThe Daniel Defense Big Hole Flat Top Upper is designed and built with a .315 front pin hole to fit the early Colt lowers with .315 front holes. This eliminates the need to use an offset pin, which requires 2 screwdrivers during assembly / disassembly of these rifles. This upper comes with our .315 Push Pin, which makes the assembly / disassembly of the upper and lower quick and easy. It has a detent ball to hold the pin securely in place. Features:7075-T6 AluminumMil-Spec Type III Hard Coat AnodizedM4 Feed RampsT-MarksForward AssistDD Logo Laser Engraved on Left SideIncludes .315 Push Pin with Ball DetentMade in the USA! Daniel Defense Big Hole Flat Top Upper Receiver w/Feed Ramps 04-012-09001