The RE 8 motor has a diameter of 8.0 mm, length of 16 mm, and weighs less than 4.0 grams. The motor shaft is as thin as pencil lead at only 0.8 mm in diameter and turns in two sleeve bearings. The shaft is ceramic and in some ways superior to a steel one, as its electrical insulating properties allow for a very compact commutator design. Precious metal brushes also ensure constant and low contact resistance between brushes and commutator, even after a prolonged standstill. The lightweight rotor has very specific advantages, such as low inertia and very fast acceleration.