Overall score is mainly ability to prevent buildup and handle simulated heavy and severe rainfall, and (for do-it-yourself systems) ease of installation. Displayed scores are rounded; products are listed by precise overall score. Buildup is based on leaves and other debris over 16 months outside with no upkeep. Heavy flow is ability to contain equivalent of 3½ to 4½ inches per hour of water over typical roof section. Severe flow is ability to contain equivalent of 6 to 7½ inches per hour (short bursts in a thunderstorm based on National Weather Service data). Ease of installation includes need for cutting, drilling, and other work. Price per foot is price we paid for product and installation for pro products and, for do-it-yourself systems, approximate retail for product only.