The Vortex V-Series fans combine high performance and quiet operation. This fan is powered by a permanently lubricated and balanced external rotor motor equipped with a mixed-flow empeller. This impeller is a cross between vane axial and centrifugal design allowing more air volume than any other comparable design. The heavy duty galvanized steel and Hammertone epoxy baked finish contributes to the sound dampening and superior rust prevention. Furthermore- the V-Series fans operate at lower RPM making them even quieter. It comes with a 3 year factory warranty and are 100% speed controllable.