Modified bitumen (MB) is an asphalt product that can be applied to commercial flat and low-slope roofs. It's a single-ply roofing membrane that is reinforced with polyester, fiberglass, and other fabrics. It's also very flexible, which makes it ideal for installations with many twists and turns, such as chimneys and skylights. MB roofing is easy to repair and maintain because the sheets are applied in strips, so repairs are usually limited to the damaged area only. It can be applied using several methods, including torch welding and cold adhesive.