The Master Flow 6 in. Straight Oval-to-Round Boot helps provide a straight transition from an oval pipe to a round pipe or insulated, flexible duct. This boot is an energy-efficient alternative to using a stack duct. Designed for durability, this boot is made of zinc-coated, galvanized steel. The boot has a maximum temperature rating of 390 degrees Fahrenheit and a minimum temperature rating of -100 degrees Fahrenheit.