Allstar 3 inch Diameter 8 inch Length 170 CFM Rating Heavy Duty Model In-line Duct Blower is a heavy duty model with a 3 inch diameter opening and has an 8 inch overall length. The blower has a 170 cfm rating at 13.6 volts with a 3.5 amp draw. It is great for use on braking systems for extra cooling. It can also be used to provide extra cooling assistance for helmets or anywhere else forced air is needed..