Rain Proof is an additive for any windshield repair resin to make the resin waterproof. Just add 1 drop to 3-5 drops of resin into your injector and stir with a toothpick and the water in the break will be absorbed and dissapated by this custom made chemical formulation (patent pending). You no longer have to dry breaks out with a heat gun, blow dryer, lighter or dry star. Now in just seconds you can make your resin waterproof with one drop of Rain Proof. One bottle will do 60 stone breaks.