Some has asked us how to tell if you have lead or rubber flashing. Basically, if your flashing looks metallic, wrinkled, grey, and has a beat looking top, its probably lead. Rubber will always just be a pipe. It is usually white, but sometimes its black, and rarely its painted.
So if your vent isnt just a pipe sticking out of your roof, its probably lead. If you go on the roof you can see for sure. Lead will be a sheath around the vent pipe, rubber will be a simply grommet around a pipe, usually level with the roof line.