Oddly enough, this was one of the most effective camouflage helmet covers issued by a military. Why? Because it breaks up the standard round silhouette of a helmet, and makes it look more like a pile of leaves/brush. These covers are made of thicker radar screening vinyl material reinforced with cotton. I personally have one of these on my ECH in preparation for a "Red Dawn" sort of scenario. These can be applied as-is, or cut up in to pieces to go further with the breaking up of the helmet's outline. Either way, these are a very simple, yet highly effective piece of equipment that I personally endorse. If you buy multiples, these are fantastic for camouflaging plate carriers and other gear as well without having to pay out the ass for radar screening.
These have popped up in armed conflicts around the world from the Balkans, to Southeast Asia, to Africa. They are highly effective, and popular for a reason. These fit on most styles of helmets, and if they don't perfectly fit, can be tinkered with and adapted to fit.
NOTES: These are all used, so expect fading, drawstrings missing (although most seem to be present) different shades and materials (all seem to be a variation of brown/O.D) and such. That's just so there are no surprises. HELMET NOT INCLUDED.