and the back wiring on these receptacles is perfectly safe to use unlike the "back stab" receptacles in which you just stick the wire in and it is supposed to stay there. the difference is that the spec grade receptacles have a screw that tightens a clamp on the wire, whereas the back stap receptacles just have a spring that is supposed to hold the wire in. the back wire receptacles with a tighening screw are very convenient to use, and also safe.