I had purchased a whitening kit previously and could not find my gel refill. This was something I researched to make sure I could find a gel that would work in a timely manner like my previous gel. This gel did exactly that. Within 3 days I could significantly tell a difference in shading. My teeth were not severe. However, the daily coffee and other foods do take their toll on the whiteness level. This took the dullness and the staining of all of that away. I used one tube within a week, using the product nightly. Then I took one week off to cut down on any sensitivity. I did this as a precaution, because I did not experience any irritation. I'm a skeptic so it meant something to me for this to work well enough to write about it. It does a great job, expecially for the price. It is worth it.