Stop leaks and cracks in their tracks with Everbuild Black Jack 903 Bitumen Trowel Mastic. This versatile, trowel-applied sealant is perfect for a variety of surfaces, including mastic asphalt, roofing felt, corrugated iron, metal guttering, and downpipes. Its heavily filled, fiber-reinforced formula provides superior strength and flexibility, while the black finish blends seamlessly with most roofing materials.