I use the spin brush all the time and am very satisfied with the product. You have to buy the entire spin brush to start. The will last around one month and then the batteries and the brush both need replacing. You can tell when that needs to be done by the way the brush not longer moves as it did at the start. If you wait too long it will not spin the brush at all. At the same time the batteries die the brush starts to feel soft. That is you clue to replace both the batteries and the brush. Replacing the brush is very simple. You just twist the head and the brush comes off. (Replacing the batteries is not as simple. You have to work to remove the end cap.) The replacements come in a pack of two. They are priced about the same or a little less then the full brush you purchased first. If you watch they are frequently placed on sale so for less than the price of the full unit you get two brushes and two more uses out of the spin brush. All in all a good deal on a good toothbrush.
Bella Vista, AR