The EVOLUTION 4 is the most powerful under-cabinet hood provided by BROAN, that's why we classify it as a high performance range hood and not just your typical under-cabinet hood. It comes equipped with a precision balanced centrifugal blower that delivers unsurpassed quiet operation and power. On boost setting it moves up to 630 CFM and is ultra-quiet at less than 0.3 sones on working speed! The EVOLUTION 4 has a four-speed blower control to allow for superior power when needed and under all circumstances provides the ultimate in quiet and filtration.