no they don't

Beach Boy:

I am kind of biased toward them.....but I will answer this somewhat. I personally have both types.

They have single heat shields in them. In my opinion you are not giving up anything as compared to the colt shields....unless you just HAVE to have the colt name.

We use them in our full auto 9mm and 223 uppers without a problem.

M4 Aiming At U:

Derek at Azec arms has done some camo painting on our lowers and it came out looking great. with the way the plastic is injected into the molds, it is impossible to get multicolor injections.

The CAV M4 handguards are very heavy-duty, fit very well (very snug with no play), and have single aluminum heat-shields.

The Colt M4 handguards have dual heat shields.  This helps insulate the hands better, but allows much less airflow, meaning it takes much longer for the barrel to cool down.

I think I'm gonna remove the double shield from one of my Colts and stick it in the bottom of the CAV M4 handguards in place of what's there.  That will give me a double shield on the bottom, and an single on top, which should improve airflow without reducing the insulation for your hands.

BTW, I got the tan furnature, and am working on getting a compressor so I can airbrush some 6-color desert camo on my rifle.  :)

-Troy