... two options, one is single speed, one is variable speed circulation.Product descriptionStainless steel casing, big air flowing ... performance, low noise, low power consumptionSingle and variable speed models are available.NameModelVoltageFrenquencyPowerRMPAir flowFLC circulation fan ZLFJ400220V ... 110V 50HZ 350W 1380r/min5700m3/hFLC Circulation fan variable speed ZLFJ400T 220V/110V 50HZ 45-100W 780 ...