Crest 3D White 2-Hour Express Whitestrips: * Whiter, Brighter teeth in 2 hours * Whiter teeth that last 3 months * 12 month supply * Enamel safe * Advanced Seal, no-slip technology that allows you to talk, drink water and go about your day while you whiten * People sensitive to teeth whitening may experience some sensitivity due to longer wear time. If this persists, we recommend using Crest 3D White Gentle Routine with less whitening ingredient concentration.