Hard hat shells can be manufactured in a variety of materials. Most are made with some form of thermoplastic; either polyethylene (HDPE) or polycarbonate. They use these materials because they are lightweight, strong, and easily molded. They can, however, be made with other materials such as fiberglass, resin-impregnated textiles, or aluminum.
Hard had suspensions will often consist of strips of woven nylon webbing and bands of molded HDPE, nylon, or vinyl. Type II hard hats will often have an additional polystyrene foam inserted into the cavity around the suspension.