Thermo Sleeve 12ft 2.1/8″ – 2. 1/2″ Thermo-sleeve is the combination of a high temperature fabric laminated to a highly reflective mylar foil. it provides protection from radiant heat for hoses and wires. thermo-sleeves ultra lightweight construction provides more insulation than traditional bulky rubber-coated fibreglass. the aluminised sleeve reflects more than 90 percent of radiant heat; it is fireproof and oil resistant.