Peter Jones 1 I have used Panasonic's Doltz toothbrushes for 20years. I had a more expensive one with springs in the heads, but when that died, I bought a slimlIne one which takes these heads; big mistake.When you actually touch the heads, they don't feel hard, but when you turn on the appliance, there is obviously some conflict between the speed and intensity of the vibration and the material of the bristles in the head, or their proximity to each other.The result of this poor design and lack of proper testing is that the bristles/brush becomes FAR too hard when used at full speed - it bounces off the tooth and feels like you are either having a filling, or going to strip the enamel off your teeth! Change the speed to slow and they become softer, but at that speed , brushing is painfully slow and feels more like a regular toothbrush, than an expensive electrical one.