There are plenty of non-KAC RAS'es on the market too. Last time I was at KAC I saw one that was a dead ringer for a M4 RAS until you took it apart and started measuring. Material quality was not the same and it didn't fit right, but it was remarkably close visually.
Buyer beware. KAC can tell the difference so when they get them in for warranty, the outcome will not be good for the buyer.