GO SMILE Extreme Duo Kit in Beauty: NA. GO SMILE Extreme Duo Kit in Beauty: NA. The Extreme Duo Kit contains two of Go Smile's best-selling products in a portable metal tin. Get an extreme whitening boost with 14 Extreme White serum ampoules while you maintain that white smile with the On The Go Teeth Whitening Pen. Achieve a whiter smile without strips or trays and no sensitivity.. Targets concerns of tooth discoloration. Formulated without parabens, sulfates, or phthalates. Vegan and cruelty-free. Set includes: Teeth Whitening Pen (0.04 oz) and 14 Extreme White Ampoules. Brush a thin layer of whitening serum onto the front surfaces of your teeth, focusing on areas with darker stains and avoid gum lines. Don't eat, drink, or rinse for 20 minutes after applying it. GSMI-WU9. GSK052. Based in the San Francisco Bay Area, GO SMILE has helped whiten over 32 million smiles. They were created by a dentist and their products are known for their cutting-edge innovation, ease of use, and award-winning results. GO SMILE has revolutionized at-home and on-the-go teeth whitening by making it possible for consumers to achieve professional results without the hassle and expense of going to a dental facility. Their mission is simple: A healthier, cleaner and whiter smile for everyone.