Designed to expand up to 5 times in volume after dispensing, 3M Fire Barrier Rated Foam FIP 1-Step is a two-part urethane, smoke, sound and firestopping foam. This intumescent foam can be used to fill the annular space created by pipes and cables penetrating through fire-rated construction. Its an alternative to mineral wool and sealant, bricks, pillows and runny, ineffective foams and is UL listed.