MORE than I am disappointed by this purchase as replacement heads have a lifetime of only 8 to 10 days: in fact, is the bottom of the brush head is dislocated completely (this happened to me) is that is the upper part of the brush that keeps making rotations: there are more than the lower part of the brush that moves ... I bought into 24 (3 × 8 Replacement heads) in December 2013 and it I'll have to buy some, it's amazing. I am very disappointed!