Review (5/5): The best
I use 20% once every few weeks. When I get lazy and skip a month or 2, I reach for my 35% - 2 or 3 days in a row. When I really need an instant boost, one or 2 treatment of 45% easily does it. It's best to invest in bleaching trays. They last forever. Opalescent is what we use and recommend in a dental office. It is what works.