durable and amazing results [SEP] i bought these because you know coffee stains after drinking coffee for years and not brushing my teeth when i was done drinking coffee for the day had taken a toll i wish i had taken before and after pictures because there was totally a difference and people cannot see my coffee addiction on my teeth anymore they are easy to use and unlike some other ones i have tried the whitening strips did not hurt my teeth these strips were very durable and came with such better instructions than the name brand ones i have tried before i highly recommend these and you will be surprised at the difference they make in just weeks