Pipe Flashing
Pipe flashing, sometimes referred to as a roof boot, is manufactured to seal tightly around small ventilation pipes, plumbing, and other vents and equipment that protrude from the roof of a home or commercial building.
The base is typically a flexible metal so that it is compatible with virtually any roofing material. The top is made from EPDM rubber or silicone so it will slip on to the pipe like a boot, which is where the name roof boot comes from.