The Contoured Brush Heads Fits Along The Gum Line To Gently Clean And Massage Gums. Align The Brush Head So The Bristles Face The Front Of The Handle And Firmly Press The Brush Head Down On The Metal Shaft Until It Stops. Reminder Bristles Let You Know When To Replace The Brush Head. After Three Months Of Normaal Use Bristles Exhibit Fatigue, And Brush Are Less Effective. Replace Your Brush Head Every 3 Months. Compatible With Flexcare+ Flexcare Healthwhite