"AeroDuct" types meet applicable FAA and military specifications.NEOPRENE IMPREGNATION (Stocked in 10-foot lengths): CAT - 1 ply neoprene impregnation fiberglass with very closely spaced spiral coper-coated high carbon steel wire inside, exterior wrapped firerglass cord. From -65 to over +350 degrees F. Aircraft type.SILICONE IMPREGNATION (Stocked in 11-foot lengths): SCAT - 1 ply same as CAT except with silicone rubber impregnation. From -80 to over +350 degrees F. Aircraft and industrial type.SPECIAL NOTE: Odorless and non-toxic ducting is important in heat and vent systems. AERODUCT neoprene and silicone ducts have been fully tested by civilian, commercial and military aircraft manufactures and approved. Buna ("nitrile") types have odor at elevated temperatures.NOTE: "Wire Spacing" (WS) is the dimension from the crest of the wire in one coil to the crest of the wire in the next coil as shown.