Bought mine at a local roofing supply. Peel and Seal. I think it was about 18" wide by 33 ' long. If I remember it was about $25.00 per roll. I was also worried about it sliding on the vertical surfaces and on the roof so I used some 3m Super Adhesive as added adhesive. That stuff is definately stuck on now. Ive had to remove a few small areas and basically had to chisel the stuff off. Sure made a difference when I shut the doors now. No tinny clang.