The materials covered by this specification are intended for thermal insulation only and may be used in either sheet or tubular form. In tubular form, the insulating material is intended for piping systems operating at temperatures from minus 20 to 180°F. This material has low thermal conductivity, is a good vapor barrier and is serviceable at operating temperatures. Material covered by this specification may vary in thermal conductivity depending upon the manufacturer. The minimum wall thickness to prevent condensation will therefore vary (see 3.2).