Locking Devices, Twist-Lock®, Industrial, Flush Receptacle, 30A 125V, 2-Pole 3-Wire Grounding, L5-30R, Screw Terminal, Black. Wire restraint recess for both back and side wiring, greatly reduces the possibility of loosening the terminal connection Face color coding by voltage facilitates locating and mating of proper devices All-brass mounting and grounding system provides a lower resistance ground path and greater resistance to corrosion than steel mounting systems