Leitner-Wise (later LWRC) .499 LWR caliber, 16 in black stainless barrel with integral muzzle brake. The quad rail at the end of the handguard is not the gas block it is under the handguard. Has the number 67  hand stamped on the bottom of the gas block. The coastguard tested these uppers for use on m16s as a mini 50 cal. The upper is in great condition with a great bore but does have some small scuffs on the quad rail. Kinda neat piece of history