The hole for the wire is about 4mm, I don't know why people say it's so small. I have one complaint that the cap is made of a harder plastic. So when I crimp the wire the cap may break or not stay in place. Since I need it for a tiny, tiny wire from an adhesive pad like TENS, I just roll up part of the pad and stick it in there. I did it with a smaller clip and it works great. Yes I always abuse things which drives the hardware store guys crazy! "You want to do WHAT with him?"