The Hydro 3 Blades shave very well and safely, have me so never cut and the hair can be reliably removed. I think that 3 blades also completely sufficient. The blades can be flush also very easy, because you can get through from the back water. A disadvantage, however, that the blade is a little large by the integrated gel strips. Especially under the nose, it is thus more difficult to remove all the hair. One can not fold back as the more expensive blades Hydro5 the gel strips. Sometimes, especially when the blades are new, comes out as too much gel from the gel strips, but apart from that it's a waste, is not a major problem.
Well, I think that the Hydro 3 and the Hydro 5 Blade are compatible, so can be used on all hydro-shaving.