This hose connects the two large outlets on the fan shroud to the heater boxes on all Type 1 engines. The hose is held in place using two large hose clamps. Also known as a fresh air hose or tube, it has a 2″ inside diameter (to fit over the port on the fan shroud) and is roughly 40″ long so typically one hose can be cut in half and used to fit on both ports. The flame resistant hose is can withstand up to 450 degrees fahrenheit.