I first got these at my dentist office after my six month teeth cleaning. My teeth are already more white than yellow, even though I am in my sixties. Non-smoker, coffee with creamer and sometimes iced tea drinker. I found these whitening strips make them even whiter, and removed a some stubborn minor staining on my lower front eye teeth near the gum line. They are a little tricky to put on so go to YT for how to video so you don't waste any. Be sure to gently push the strips between the teeth to get the full whitening effect. I used them for severn days and it was good enough. I waited a week and did another seven day treatment. Results are amazing. (Side Note: if your teeth have a gray tone to them these will not work. When teeth turn gray its due to enamel erosion. Whitening products cannot turn gray to white.)