U.L. Classified. Code Approved. Seal penetrations of plumbing, refrigeration and AC lines, ducts, vents and electrical cable through fire-rated floors, walls and ceilings. Easy-to-use, non-shrinking, non-toxic and permanently flexible. Blocks fire, gas, smoke, air and water migration. Use ceramic fiber filler together with putty or caulk for thick penetrations. Technical bulletins available.