Both are effective, so we advise that you purchase either of our Whitening Strips, depending on what best suits your needs.  Our Leave-In Whitening Strips must be worn for at least 60 minutes for optimal results, while our Dissolving Whitening Strips are only kept on for approximately 15 minutes, before disappearing.  These Strips are great for those with limited downtime and wanting to whiten on-the-go.