Yup, I got the same one when I was going to make a red laser, don't buy it if you haven't bought it already. It might look like you can fit everything, but once you open it up, there's a lot less space because it has 4 plastic things in the corners to place pc boards. Plus the things where you put the screws aren't all the way in the corners, they're more in the middle and you loose some space. You'd have a hard time fitting the rheostat in there if it didn't have all that crap inside of it, but with all of that it's impossible. I tried to cut all that off and melt it with my broken soldering iron but I messed up the box and now it's all crooked. Get another one, a little bit bigger since you'll be using the rheostat, it's big as hell, just google plastic enclosure and you'll find some pretty decent ones. 
