This Smile Sciences kit uses recently developed technology with a smarter and rechargeable LED light. In addition to a blue light which reacts with the gel to enhance the whitening effect, it emits a red light which reduces bad breath and kills bacteria. The light has a 15 minute blue light timer and 10 minute blue/red light timer built in. In addition to the LED light and tray, this kit includes: Three teeth whitening pens (14 treatments each) Power cord for charging the light Shade guide Instruction manual Stronger gel 35% Carbamide blend The pens have a shelf life of one year from date of purchase. Ingredients: Carbamide peroxide, potassium nitrate, glycerol, propylene glycol, deionized water, carbomer, carboxymenthyl, polyvinylpyrrolidone, sodium hydroxide, menthol. If pregnant or nursing consult your OB.