workswhen it does [SEP] the kit includes gel and the rechargeable led unit i was able to use it for a few days and then the main led unit stopped taking a charge and it will no longer turn on i had to return itwhen it works it made a noticeable difference and did so without any pain or increased sensitivity normally my teeth are very sensitive and in the past other whitening products hurt too much to use this one was great in that regardno pain at all