A far better alternative is available.
When I used these strips, I found that they were too flimsy, and therefore tended to bend back over themselves, making them difficult to apply.  After they were applied to the teeth, they did not always stay in place and tended to slide around.  Also, it is inconvenient to have to remove the strips, when they have done their work.  For these reasons, I do not consider them to be the best alternative.  A much better alternative is the dissolving whitening strips manufactured and distributed by CVS Pharmacy, Inc.  These strips are less flimsy/ more firm and therefore don't stick onto themselves, they adhere to your teeth far better; AND they dissolve completely in about 5-7 minutes, leaving no messy residue or plastic film to have to discard.  On size strip (larger than Crest's) fits both upper and lower teeth.  The active ingredients are the same as Crest, but the cost is about half the cost of Crest.  Superior to Crest in every way.
Rating: 3 stars