Z-Stop, a zinc strip (50 feet roll) that's easily installed on your roof, acts as a barrier to roof moss, algae and fungus growth, protecting the roof, its appearance and value. Z-Stop is a zinc roof moss, algae and fungus inhibitor that is applied in strips to old or new roofs. It works with any wood or composition roof. The natural action of rain water time-releases zinc carbonate, a proven fungistatics, which then washes down the roof preventing destructive roof moss, algae and fungus growth.