Replacement vacuum motor brushes are sold individually and each motor uses two. Occasionally only a single brush may need replacing because only 3/16" of carbon is left on one but is longer on the other. Replacing brushes that have worn all the way down and scored the commutator/armature will wear down fast and be of little benefit. Therefore, we recommend replacing the motor if the armature has been at all roughed up. Also, once a motor has run its life expectancy of about 800-900 hours it is best to replace the motor, not the brushes. Note that 120 and 240 volt brushes are not interchangeable. Read more atChecking and Replacing Motor Brushes.