Nylon construction, Back wire Dead-Front design Neoprene gasket seals cord hole from dust and debris Inserts included for three separate cord grip ranges Back wire terminal clamps for easy secure wiring Individual wiring compartments with tapered channel for easy insertion of wires Clear cover over wiring compartments allow easy inspection of wiring terminations Combination head screws standard - slot/Phillips in the U.S 20 amp - 125/250 volt NEMA L10-20 Boxed .250 in.-.690 in. cord diameter