**OM 01 and 02: We stand for Hygiene. "People are concern about oral hygiene, BUT ignore bristle hygiene." Making them standable/hangable, we have a reason behind. Most people like to place their toothbrushes in a bathroom cabinet or on a countertop. And, of course, you know that is not hygienic! A toothbrush having a big head size and a very dense bristle field can accumulate a lot of bacteria on. So, the worst thing about it is the bacteria can be put back into your mouth. That is why we have to make them standable for bristle hygiene. You don¦t need to let the bristles touch any surface in a humid environment like bathroom. **OM 04 and 08: We reach deep. "For effective cleaning, choose proper brush head size". People, women and children, having a small mouth will not feel comfortable when using conventional toothbrushes. We know that. We designed OM 04 and 08 to have a little head size with a slender handle. The head, small and rounded, is comfortably fit in your little mouth. A slim handle allows you to reach deep to the back of the teeth. And with soft bristles and an elastomeric-flexible handle, you can give a gentle massage to your gum while brushing.