I just got my flat top upper today from Bushmaster, that I had been eagerly awaiting for a month, to finish my M4 project. Lo & behold it has RAS numbers! Even numbered from 2 to 12, rear to front. Too bad I'm going to cover them up with a GG&G FIRE rail. I also have a RIS that is going on the gun so, they won't match numerically anyway but it is COOL!