LOVE. Get that Cali girl bright white smile. Results are fantastic. Warning: If you have sensitive teeth you may hate this product. I never noticed sensitivity before this, but did in the hours after using a strip. The directions indicate that if you experience sensitivity you should not use twice a day and maybe use something like once every couple days. This really helps. Also, I brush with Sensodyne PRONAMEL during the couple weeks I am using the whitening strips. These two tips eliminated any sensitivity and I still had great results. It was at least a year before I noticed a less white smile, and then I just bought a new pack.