Diamond-shaped bristles provide a greater surface area for an exceptional cleaning and whiter teeth teeth in just one week. The uniquely designed diamond bristle heads have 44% more bristles than Philips Sonicare's standard sized ProResults, providing you with both superior plaque removal and whiter teeth. The bristles are medium/ stiff, delivering a firm yet gentle cleaning experience, and the bristles gently fade in use to remind you when the brush head needs to be replaced. Please Note: 4 brush heads per pack. The AirFloss nozzle was designed to optimize user technique. The guidance tip makes it easy to find the spaces between teeth and to place the tip at the appropriate horizontal angle for maximum cleaning. It is recommended that you replace the nozzle every six months to prevent hard water build-up and reduce the potential risk of bacteria build-up.