These do a great job at whitening your teeth. One tip I recommend is getting a pair of scissors, cut the strips out without peeling them, then with a sharpie pen trace the strips to outline your gums and then cut the strips to where they ONLY make contact with your teeth and not your gums; this will greatly reduce the amount of sensitivity you will get from using the strips. However, you will not be able to stretch the strips or else they will not accurately adhere to your teeth. Side note: fold the strips in half to get an idea as to how to center the strips on your teeth and use a mirror when tracing your gums with the sharpie pen. If you want even BETTER results, purchase a blue LED teeth-whitening light: wear the strips as directed, then, with the strips still in place, use the light for about 5-15 minutes, then take everything off. Try to invest in a sensitive toothpaste which you should brush with promptly after whitening.