Hydrofarm's Fan Speed Controller was designed especially for centrifugal fans. This means it will help prevent damage to fan motors, ensuring longer life. (Meant for use with brushless motors, and all Hydrofarm inline fans, not booster fans). It will correctly and precisely adjust the speed of centrifugal fans. These controllers are more sensitive than any on the market, and are compact and built to last. Features : Internal electronic auto-resetting circuit breaker, state-of-the-art electronics throughout, rated for 500 Watts max (5A), 100V-120VAC voltage capacity.