What's a commutator, you ask?

The commutator is the part that the brushes rub against in order to energize the motor. It's all very interesting and if this is new to you check out HowStuffWorks for an explanation. Make sure you click the "Next" button to see the animation.
Anyway, you can see that the carbon portion of the brush is long and intact, so these will work fine for hundreds of hours.