The Carlon® SuperBlue™ Hard Shell Boxes combine the features of the hard shell thermoset box and the thermoplastic PVC style box to create a "new" rigid nonmetallic wiring box. Molded out of specially formulated thermoplastic material, Carlon SuperBlue boxes are so strong they won't crack or break, even in extreme environments. So rigid, they resist flexing and hold their shape even under the worst conditions.