The only box big enough to hold the large ends of a 30A trailer extension cord. Can be installed upside down or sideways. I only gave it four stars because the box design doesn't have a cutout large enough to accommodate those large cable ends. With the appropriate tools, you can cut a hole in the bottom of the lid big enough to accommodate it. This is a headache that could have been eliminated with a box to house those cables. Overall it does its job very well!