Yes you can wear a skull cap under a ski helmet.
Cech has a helmet that's made by Adidas. This helps protect the weaker spots on his skull. This helmet was normally a rugby style helmet, with some changes to fit cechs needs.
The cranium (the skull minus the lower jaw) covers and protects the brain much as a helmet does to protect the head.
helmet = skull cage = ribs (as in "rib cage")
what you have to consider here is that the helmet may keep your skull from cracking or braking. But while the helmet protects the skull as it is stopped suddenly (when you crash) the brain inside the skull continues to travel at 50mph and crashes against the inside of the skull, and this may kill you.
No, there's only the standard EVA helmet and the design of the helmet with a skull carved into it.
tigrix skull shell
Skull
First, rank up until you get to Major, then buy the EVA helmet(It is required or the EVA (C) won't be unlocked). Then, rank up until you get to Commander and EVA (C) or Emile's helmet will be available for 120,000 credits.
You unlock Emile's Skull helmet by reaching Major and purchasing the E.V.A. base for 30,000cr, later on E.V.A. [C] will be revealed once you hit Commander and will be available for 120,000cr.
the hard structure protects your nervous system from getting damagedYour skeleton protects your nervous system by providing a sort of helmet for your brain. This helmet is called your skull and it helps keep the most important part of your nervous system safe.
Its a skull with a helmet on and they're made by pro comp. The name of them are metal mulisha.