It is very strong so start low, even before the indicators. There are professionals who say it is a gimmick so buy it if you really want to. It didn't harm my skin but you do become red. I use it with a gauze between my skin and the glass. It doesn't come in a box so make sure to keep the styrofoam.
It just arrived, it seems to be good and i tested it, so far it is working. Good time shipping.