We use FN contract uppers. FN itself is like all major manufacturers, they acutally make nearly nothing themselved. They are made by the same contractor that makes FNs uppers. FN (Colt, BM, etc.) does not like to allow uppers with their manufacturer code marked on the upper due to potential liability suits from being identified as the mfg. That is why most of the times uppers will not be marked "F", only the mfg. code that comes afterwards.