I did not have a good experience with the Rembrandt 2 Hour whitening kit. It was expensive, but I have read good reviews, so I picked up a box. I realize it's called a two hour whitening kit, but for some reason I thought it would be less. I assumed the name meant it was comparable to a two hour whitening. I was wrong! You actually have to leave these trays in for two hours. The trays are uncomfortable. I put the gel in, but I didn't want to put too much because I didn't want it to get into my mouth. The trays started to hurt my gums, but it was bearable. After twenty minutes, my gums started to burn. I didn't want to give up on the treatment because I had spent so much money on it. I decided to tough it out. When I was finished, my gums were throbbing. They were bright red and swollen too! My teeth looked strange. They had spots of them that were really white, but the rest of them were the same. A few hours after I was done, the white spots were gone. My teeth were back to the way they were before I started.