Features Designed to optimize performance Reminder bristles ensure you are getting an effective clean Reminder bristles let's you know when to replace the brush head. After three months of normal use bristles exhibit fatigue, and brush heads are less effective. Replace your brush heads every 3 months. A brush head that fits multiple handles Screw-on brush head for our original Sonicare handles Screw-on brush head that will fit our original Sonicare handles Easy to maneuver to focus on hard-to-reach areas Unique angled neck helps you reach back teeth The slim angled neck enables you to easily maneuver the toothbrush head, particularly in hard-to-reach areas to remove plaque.