Oral-B iO Ultimate Clean Electric Toothbrush Heads, Pack of 8 Black Replacement Heads, Removes 100% of Plate, Designed for Your Oral-B IO, Fits the Letterhole'COLOR CHANGING BRISTLES: Oral B replacement brush heads have color changing bristles to signal when to replace them to restore 100% more effective cleaning' REPLACE EVERY 3 MONTHS: A worn out toothbrush head makes cleaning teeth more difficult, not removing bacterial plaque. For a deep clean, replace the brush head when the bristles change colour "EXCLUSIVE FOR IOS ORAL B HANDLES: The original Oral B replacement brush head is designed for deep