These genuine OEM replacement toothbrush heads work great and fit the toothbrush unit properly. They last a long time and they clean teeth to make them feel amazing, the way the Sonicare toothbrushes are capable of doing. Cheaper knock off replacement heads might cost less but the ones that I have tried are not nearly as good and they don’t fit the toothbrush or the head holder / cleaner to the point that they are annoying and frustrating. I recommend these to anyone that owns a Phillips Sonicare toothbrush system. The seller shipped them quickly and they arrived safely and in good condition. Thanks! A+++++