xterior Inc - Gutter Zap cleans black streaks off factory-painted metal and fiberglass-like gutters RV s etc. caused by electrostatic bonding. Gutter Zap is a Household Cleaner easy to apply. Spray on and rinse off with garden hose pressure. This product will not harm vegetation or painted surfaces when used according to directions. Gutter Zap for Commercial Use is a 100% biodegradable concentrated formula that removes heavy soil dirt and industrial stains especially those pesky tiger stripes on gutters. It contains special sheeting agents for easier rinsing. 32 fl oz. (1 Quart)