Genuine hard shell cases are typically made with several layers of durable polycarbonate. However, cheaper imitations often use other types of plastic or skimp on the layers. Polycarbonate is sold under the trade names Lexan and Makrolon.
Polycarbonate is a specific type of plastic known as a thermoplastic polymer. "Thermoplastic" refers to polycarbonate's ability to be bent and molded at high temperatures, yet solidify at low temperatures. The word "polymer" simply refers to the large, chain-like structure of the molecules, which provide the strength and flexibility of plastic at room temperature. Hard shell cases typically stack several layers of polycarbonate to achieve maximum protection. The inside of a hard shell case is often lined with foam to protect its contents from the shock of a collision.