These whitening strips remove years of tough set-in stains with the 30-minute per-day treatment. They come with a non-slip grip and are gentle for sensitive teeth. They are strong enough to remove stains. Price drops from $19.99 to $16.99 to just $8.49 when you add the code "UTJSMJFG" at checkout. Shipping is free for Prime members or when you spend over $25.