On a negative note, there are essentially three things:
1.) to tight fit, are after fitting only with enormous power again to remove
2.) resonance on color ring (of the rest ever "blue" is) interferes not only acoustically, but also reduces the oscillation amplitude
and so the cleaning power. The workaround I put the brush head not quite on - is Grawitschko solution.
3.) bristles are too soft
Is an original brush wear, you will notice this immediately when a new original brush:
this feels is namely equal harder than a worn.
Not so, however, these "compatible" brushes: a clear sign that they are softer than the originals.
In sum:'ve saved and paid dearly on the wrong end.
