Exterior Inc - The Gutter Zap Gutter Stain Remover is formulated to remove black streaks from gutters caused by the electrostatic bonding of tar and asphalt. Gutter Zap cleans black streaks off factory-painted metal and fiberglass like gutters RV s etc. caused by electrostatic bonding. Gutter Zap is 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 Residential 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. It was now coming in a commercial concentrated formula. Net Quantity: 32 fl oz. (1 Quart)