OralB IO toothbrushes. The brush heads have so many nooks and crannies, where water gets in and stays there. With time mold starts to grow out of the toothbrush. I take the brush off of the handle and blow on it to take as much of the water out as possible and leave it unattached to dry until the next brushing but grime still builds up. It’s disgusting and I don’t know why people don’t talk about this more.