I have a fleabass street bass, and I need to replace the nut because it was cut to much. Does anyone know the exact size needed? I do not have very good measurement tools.
Get good "measurement tools" and you'll be able to find out. You'll need correct tools if you're going to replace it yourself anyway. If not, take it to a pro. Good luck.
How much "too much"? If one string is just a little low, you might get by with a drop of super glue. Obviously, you need to let it completely set up before you string it!