In reality this supply should last a week, if used twice a day. This might seem like a good alternative for people who would like for a "touch-up", but as a previous reviewer pointed out, these strips didn't seem to be that potent. I didn't even feel my gums tingle. I guess that would be good if I saw some teeth whitening; I didn't. I couldn't find an experimentation date on the box I received, so I wonder if these strips have been sitting for a while and in the process lost their potency. To be fair, I'm not sure that is even a valid concern. I just know that I didn't seem much of a change after a week (using the whole supply) and did not observe any of the usual effects (tooth sensitivity, sensitive gums) that using strips with higher H.P. concentration should produce. Those observations coupled with those of another reviewer suggests that these strips are not the best alternative out there. Please consider my comments for this listing of Supreme PRO. I can't comment on the potency of other whitestrips or other supplies of Crest whitestrips supreme professional.