Kevlar helmets have a purpose.

I once took down a drywall interior wall with one. Beat the wall silly I did. MOUT training, and I needed to get from room A to room B w/o going into the hallway. Considered using my rifle, but gypsum is a bear to clean out of the buttstock.

As to the sizes, I remember S/M/L only. None of them fit worth a crap, and jumping in them was a pain, as they would slide around no matter how tight you had them, especially during a Jumpmaster door check.