messy ineffective [SEP] let me just start off by saying if you have a white sink do not even think about buying this product it does not matter if you have running water going and you spit right in the sink or if you spit it out with running water a foot away from the sink it is going to go everywhere black dots everywhere i see zero difference weeks in from using this product i would just spend an extra or bucks and get crest white strips if you do not believe me buy it and you will find out the hard way