1 Roll-4"x50'. Seals an average of 50 square feet based on 16" oc. RainEscape Butyl Tape is a self-adhesive butyl waterproof flashing material designed to seal out moisture around RainEscape Troughs and Downspouts. RainEscape Butyl Tape can also be used as an uderlayment to seal joists, and other openings under brick, siding, stucco or wood - anywhere a waterproof seal is needed.