DOES NOT WORK FOR LONG [SEP] I used the Glo system for a week and it worked great! I was very satisfied. I received the product in April 2022. It is now July 2022 and I bought a set of 3 teeth whiteners to refresh my teeth. The machine does not work very well now. It may work for one or two times, but not the whole four times. I charge it until it's completely charged and it maybe lasts for a couple times instead of the entire four sessions. I'm wasting the product because I put it on for the next treatment and the machine dies. The whiteness did not last so long either. It's not hard to use and it worked when I first received it, but it's a lot of money to have it work only for a week.