Camco 15 Count Orange Holding Tank Treatment Drop Ins. They are designed to eliminate odors and break down waste in RV or marine holding tanks. Each drop in treats a 40-gallon tank, making it convenient and easy to use. Simply add one drop in to the tank and let the citrus power work its magic. The fresh citrus scent leaves your tank smelling clean and refreshed. Environmentally safe and contains 15 treatments.