Protective helmets used for recreational purposes in the nature of biking, skateboarding, inline skating, non-motorized scootering and sledding; protective helmet systems comprised of a base helmet with a securing chin strap, with an adjustable fit inner-liner, and with interchangeable outer shells, all used for recreational purposes in the nature of biking, skateboarding, inline skating, non-motorized scootering and sledding; Interchangeable outer plastic shells for protective helmets used f...