Whiten your teeth while you sleep: the Colgate Optic White Overnight Whitening pen removes 15 years of stains in just 1 week when used as directed (two weeks of treatment is recommended for the best results). Each pen has 35 nightly treatments, with an enamel safe formula containing 3% hydrogen peroxide. It is designed for no tooth sensitivity during and after the whitening process. It's easy to use: click the back of the pen and apply the unique formula onto clean, dry teeth. The formula dries within seconds, and will stay on your teeth while you sleep. To remove, simply brush your teeth when you wake up the next morning and enjoy a whiter smile.