These are terrible!
I normally buy replacement heads at BJs but thought I'd try these.  Out of 4, one lost its innards (stuck to the actual unit, while outer shell came off), one couldn't connect firmly to the base, and the other 2 slide on and off at will, adding an extra special challenge to the otherwise boring task of brushing one's teeth.  So, if you enjoy the added excitement of wondering when the power tool in your mouth will develop leprosy, go ahead and give these a shot.  I won't buy them again.
Rating: 1 stars