Variispeed Fan Controllers are easy to use fan controllers for controlling single fans (excluding the considerably more expensive and powerful EC fans).
They can control the fan from 0-100% (though most fans should be run at 35% plus when using this technology) and can take up to 300W, which covers all of the CAN RK fans that we sell.
The Variispeed is well built, simple to use and very cheap - they are a great way of taking the edge off slightly too powerful fans without the need to replace the whole unit.