The ZIRPOR family of microporous insulation has a thermal conductivity one tenth that of ceramic fiber insulation. ZIRPOR-1 has a bulk density of 0.30 to 0.35 g/cm3 (18.7 to 21.9 lb/ft3) and has a maximum operating temperature of 1740¿F (950¿C). ZIRPOR-2 and ZIRPOR-3 consist of pressed sheets of the microporous insulation, which are easily fabricated into curved panels. ZIRPOR-3 has an operating temperature range from -310¿F to 300¿F (-190¿C to 150¿C). ZIRPOR 4 and 5 are vacuum-packed microporous insulation sheets, which are installed as backup thermal insulation in large energy-consuming refractory installations.