Above: The inner surface of the rock helmet consists of a transparent Pet G liner and a rim of EVA foam. The transparency lets you see the inner workings of the helmet and this acts a design feature as well.
The Foam padding is then used to provide a comfortable layer between the helmet and the users head.
Above: The closer look at the paper liner. By using more ribs we can considerably reduce the thickness of the liner and thus make the helmet fit closer to the head.
