I wanted to gently whiten my teeth slowly, and they were pretty yellowed after 63 years on the planet. I was resistant to having the quick whitening done as I worried it would be hard on my teeth or gums (and I still need my teeth for a few more years).I have tried, without good success, the Crest Whitening Strips. They are flimsy and because I produce more than average saliva, they often came off too soon. This product has "insertion" trays that put the whitening strip in place before you remove the tray (after about 30 seconds). The whitening strips are subtantial and stay in place.The box comes with 10 sets of trays (upper and lower), I put them both in at one time, and I leave each whitener strip in for 15-20 minutes. After one box (10 trays), there was noticeable improvement. So I ordered a second box, and after using those, my teeth are now much whiter, and at a level I like. I am not looking for George Hamilton white which can blind those around you, just to look good to my wife and in pictures (you can really see the difference in pictures). So you have to balance the cost with your goals, but 2 boxes will gently do the job and still be much cheaper than the "professional" one trip treatments. DON'T have your teeth whitened at the county fair or on a cruise ship! Your teeth are too important.