Outside air unit is commonly mounted inside the driver compartment on vehicles with windows or closed compartment to provide forced, filtered air to the driver for cooling and to help prevent shield fogging. Intake top can be used with 1-1/4" helmet hose or trimmed to accept larger 3" hose, such as ALL42150, routed to the motor from outside of the car or fastened to a plastic duct, such as ALL42143, for fresh air. Motor has two speeds and is recommended for 12 volt systems.