Braun Oral B iO Gentle Care Replacement Brush Heads has 4000 filaments for a gentle and effective cleaning experience. Oral-B iO Gentle Care series combines powerful, but gentle micro-vibrations with Oral B unique dentist-inspired round brush head design for a professional clean feeling every day. Optimized bristle patterns adapt to the curves of the teeth and gums, but are extra soft for maximum comfort. With a specially-designed overlay of concave and convex bristle trim patterns, the Gentle Care Refill precisely adapts to the curvature of the tooth and gum line for your deepest and most thorough clean. iO technology Combines Oral-B unique round brush head with the gentle energy of micro-vibrations for synchronized cleaning action. The cushioning outer ring of bristles has the smallest diameter bristle filaments to be extra gentle to protect sensitive teeth and gums. Oral-B signature round brush head, bristles are specially configured to best surround each tooth for the best possible clean. The only refill brush heads designed exclusively for-and guaranteed to fit -your Oral-B iO