Just like the manufacture heads at a fraction of the price.
We have had a sonicare toothbrush for years and the price of the heads has always blown me away.  The manufacturer wants about $10 a head for replacement brushes.  These offer you the same quality as the manufacturer at a fraction of the price.  Using one right now (well this AM) and I cannot tell the difference in feel or performance.  Highly recommend you check these out instead of paying crazy prices that sonicare wants for replacement heads.
Rating: 5 stars