Philips Sonicare Optimal HX6064 / 10 spare heads 4 pcsThe Philips Sonicare W Optimal White brush heads must be replaced at the 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 worn too much. This pack contains four Sonicare W Optimal White heads. They are standard size and easy to fit on any Philips Sonicare brush except