Philips Sonicare ProResults HX6018 / 07 spare heads 8 pcsThe Philips Sonicare ProResults brush heads must be replaced at prescribed intervals , both to maintain full functionality and for hygienic reasons. Ideally, replace the warhead every three months. You will also be reminded of the need to replace the special blue fibers, which turn white when overly worn. This package contains eight Sonicare ProResults heads that are suitable for both long term and novice users of sonic brushes. They are standard size