These pens are great for touch ups and can be used with our deluxe kit or another light you may have. The light does help the gel to stay in place longer but the gel can be used with out the light as well. The refill pack comes with 3 pens. Keeping them in the fridge can also extends their shelf life and keeps them potent. The Ultimate White is best for yellow teeth of people who have not had sensitivity to bleaching.