They have two different M4's - a normal light one and what they call the HBAR M-4 (like Jumbo Shrimp). I have one of each. If you phone in the order the good people there will know what you're talking about when you ask for the barrel you want.
Both have the M-4 notch in the exposed barrel.
The true M-4 is a light weight barrel, mine came in 14.5" with the Phantom pinned and welded for my pre-ban. The other I have is a 14.5" HBAR with an AK brake pinned and welded for second rifle.