VIVOSUN Variable Speed Controller Cordless Vent Blower Speed Adjuster for Fan

the description says that it's a 3 speed but it's a variable speed which is fine because you can set it for any speed you want, and for durability it's been running since I received it without getting even a little warm well worth the convenience of being able to regulate the air flow as necessary in my HOT garage.environment is everything when you have a garden in a confined space and it all starts with proper air flow, I would buy this again the price is right!!... =)

The device controls inline fan speed great! I get full range on my 130cfm from wide open full blast to barely making a breeze. This controller does make my fan produce a distinct 60hz tone when turned much lower than the begining of fast that negates any noise level decrease expected by turning the fan slower. The buzzing is actually quiet loud so if noise is a concern look elsewhere.