Review (1/5): Hydro, Maybe.  Clean, No.
The primary difference between these HydroClean heads and a full-size SoniCare head is that Philips has replaced all of the bristles in the center with two little rubber flaps. If my own experience is any indication, it's a poor trade-off. Within just a couple weeks of switching to this new head, I'm seeing a lot of buildup on my teeth... which does not occur with the original style heads unless they are overdue for replacement. I'm switching back!