Rain-X washer fluid additive. Instantly deposits Rain-X treatment every time you use your windshield washer fluid. Compatible with all windshield washer fluids. Provides outstanding cleaning and leaves a water and soil-repellent finish that reduces wiper chatter, streaking and smearing. Rejuvenates and extends Rain-X performance. Summer use: Add 4 fl. oz. to treat 1 gallon of plain water in washer tank.