These 16" XM-177 Style Upper Half with a flat top features a 11 1/2" barrel with a 5 1/2" flashider pinned and welded in place. This is a reproduction, not an original XM-177 upper half. Also features M4 feed ramps and a 1 in 9 twist. Includes complete barrel assembly. Constructed from 4140 Chrome Moly. No FFL required. Easy installation--remove 2 pins, insert upper and replace pins.