Instruct: Classify the given review as either positive or negative.
Query: Great whitening

Takes me a little longer than 7 days to use these because I have to take a day off after 2 days. Which is usual for any type of whitening I use. Best whitening I've tried. The trays stay put and have a pleasant taste. I am a daily tea drinker and my dental hygenist turned me toward these, since I can not afford professional whitening. I have tried Crest and Rembrandt products w/o the level of whitening these offer.