The Crest Advanced Seal Whitening Kit comes with 14 whitestrip packets, each of which has 1 upper and 1 lower strip. The Advanced Seal Technology helps the strip stick to your teeth, offering a custom fit without slipping. You can talk and drink water while wearing the strips. The Crest 3D whitestrips make use of enamel-safe whitening agents that are preferred by dentists. It can be used for 30 minutes once a day. It"s recommended for adults 18 years of age and older.