Anything purchased over the counter will be one size fits all and it is also limited in its concentration. These systems are also expensive for what they can do. Unless you are young with only minor stains, you will likely be disappointed. Zoom! is a professional teeth whitening system made to give actual results using custom made trays and several gel options to achieve those desired results. There is no better made way to whitening teeth regardless if you have minor stains or dark yellow teeth from the natural aging of teeth. It works!