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. Winter use: Add 4 fl. oz. to 1 gallon of any winter premix washer solvent. 16.9 oz. treats 4 gallons of water or premixed washer fluid.