Get the professional result of a teeth whitening treatment at home with Crest 3D White Strips Professional Effects, a dental whitening kit. The box contains a course of 20 applications. Each thin, flexible strip is coated with a tooth whitening gel. Designed to conform to the shape of your teeth, they work by keeping the whitening gel on your teeth for 30 minutes once a day to get at stain build-up both on & below the tooth's surface. The strips provide impressive results in just 3 days, with full, lasting results in 20 days. The groundbreaking treatment is formulated with the same enamel-safe ingredient that dentists use, while its Advanced Seal technology ensures the strips stay put through talking & drinking. Using a mirror, apply the gel side of the strip on front teeth. Wear for 30 minutes, then remove & discard. Do this once a day for 20 days, & enjoy long-lasting professional level whitening.