It's a Larue low profile gas block. The rest of the specs... Denny's 16" WOA Recce bbl, Miculek comp, Smith NM carrier. Between the comp and the barrel weight (not too bad, just more towards the muzzle than what I was used to in my M4), the rifle barely moves when shooting offhand. It's the new rifle I'm using for 3-gun matches and it rocks for hitting steel at long range.
With the design of the handguard, it gets good air flow for cooling. The first match I had it at it didn't start to get really hot until a friend shot it right after I did (her AR tooka dump and she had to borrow mine).
FWIW, for anyone lookig at getting this, the installation of this handguard is pretty easy. The only time you need to use tools is for tightening the barrel nut (naturally) and for the screws that hold the handguard on. The way that the handguard attaches to the extension makes it really easy to disassemble and clean.
And it's not purple as it looks in the picture. Something about the red rocks near by made it come out that way.