My best advice is not to use these screws. The screws come loose and once you get to work, restarting is inconvenient. I couldn't believe how much time I wasted trying to install them (I've installed LOTS of GFCIs, these are the worst). Another reason is that there is only one way to insert the wire into the hole on the back using the pull tab (not the auto crimp or external tab). Let's just say these went in the trash and I bought good quality ones from a store. I would NOT buy these.