The iO collection combines powerful, but gentle micro-vibrations with Oral-B's unique dentist-inspired round brush head design for a professional clean feeling every day. Ultimate White Refills help whiten teeth starting from day 1* *by removing surface stains. Precisely angled bristles lift and remove plaque. Dentists recommend changing your toothbrush head every 3 months for best results. Do not use on children under age 3. Replace brush every 3 months or sooner if brush head becomes worn. Medium bristle heads.