Oral-B Genuine Precision Clean Toothbrush Heads Replacement Refills for Electric Rechargeable Toothbrush, Deep and Precise Cleaning, Pack of 4The shape of the head allows the bristles to surround each tooth for individual cleaning Penetrates hard to reach areas Indicator bristles fade as a sign to replace your toothbrush head for a better clean (about every 3 months) Dentists recommend replacing your toothbrush head about every 3 to 4 months or when bristles are faded and worn Compatible with the entire line up of Oral B rechargeable electric toothbrush handles, except for Oral B Sonic