A nut driver has a socket tip that turns nuts, most often the wheel nuts on an RC car. It works like a screwdriver but grips the nut fully.

5.5 mm and 7 mm cover most RC wheel and hex nuts. Check your car to confirm, and a set covers the common sizes.

A nut driver grips all sides of the nut, so it turns cleanly without rounding the corners the way pliers can.

A correct-size driver rarely does. Rounding usually comes from the wrong size or a worn nut, so match the size and replace damaged nuts.