CRL Gunther Seal-Kwik has a safe, proven formula for protecting mirror edges from "black edge". Seal-Kwik goes on fast and easy with a sponge-dauber top, with no running, spilling or wasteful overspray. Seal-Kwik dries clear, and will not yellow or crack with age. One four-ounce bottle will cover 20,000 linear inches of mirror edge. Sealed container with dauber minimizes product evaporation and waste.