The Colt RO933 (aka the Colt Commando) uses standard M4 handguards. The pictured one is obviously an older model with the earlier stock and the side sling swivel up front. The RO933 is a safe-semi-auto version, the RO935 is safe-semi-burst and the 6933 is a safe-semi version.
I own a 6933, which I bought because I used an RO933 as a patrol carbine for a number of years. Mine has the later version stock.