Air Mask Paks protect expensive SCBA masks from damage due to casual storage, and meet OSHA guidelines for personalized equipment. Special coatings make the pak mildew resistant, a big plus when storing a wet mask. And all Air Mask Paks are made from 1000 Denier Cordura nylon, to withstand heavy use. The EP211 Air Mask Pak comes with a plastic snap hook, which can be upgraded to a metal snap hook for $0.50 extra.