As many of you know-I bought a box of them. I am now half-way through (I just counted and I have 9 of each strip left) and my teeth are definitely much whiter! I am 41 years old and was a smoker for a good part of my life and a coffee drinker, etc. I am so happy! They aren't hard to use at all and they didn't irritate my gums or anything! I am so thrilled-I can't wait to see what my teeth will look like at the end.