The Oral-B CrossAction Black electric toothbrush replacement head features perfectly angled bristles to remove 100% more plaque for a superior clean*. The round brush head is inspired by dental professional tools for a tooth-by-tooth clean, with specially engineered bristles. Max Clean Bristles change from green to yellow to signal when to change your brush head to maximize your clean. Dentists recommend changing your brush head every 3 months. *vs. a regular manual toothbrush