I asked for Crest White Strips for Christmas and got them from Santa. They are pretty easy to use but they make my teeth very sensitive. I got the good ones – 10 day supply that lasts for 18 months. I’ve used about 4 days so far but have been doing about 1/2 day every 10 days because of the sensitivity issue. So far they seem to have worked. My teeth do look whiter to me but probably not enough for anyone else to notice. I should have taken a before photo so I could see how much of a difference it makes.