A revolutionary advancement in roof patching and repair. This long-lasting rubberized repair is specially formulated to penetrate deep into areas and stop roof leaks instantly. The secret is Penetrex , a unique penetrating oil that reaches deep into the crack and forms a complete seal. With the addition of liquid rubber, this flexible, high-performance plastic cement provides a superior watertight bond that will stop problem leaks for good. Product formulated to be used year round. Leak Stopper is ideal for a variety of roof surfaces including shingles, built-up roofs, SBS modified roofs, metal roofs, and many other surfaces. It is highly recommended to reinforce larger repairs with a strip of reinforcing fabric.