Molded from non-flammable thermoplastic material. Color-matched 1/2" long steel mounting screws furnished. Smooth surface - no recessed areas to collect dirt or discolor. Easy to clean. Full weight and thickness provide high dielectric strength, minimum moisture absorption, impact resistance. Warp resistant, fit flush to wall even in problem applications. U.L. Listed. MIDI PLATES - Extra deep. Size: 3-1/8" x 4-7/8". STANDARD PLATES - Size: 2-3/4" x 4-1/2".