From the Manufacturer
Features include: Adjustable speed from 0 RPM to full speed, 3 position rocker switch-Variable, Off or Full Speed, Full power and torque at all speeds, Sturdy Aluminum Case. Go back and forth from any preset speed to full speed at the flip of a switch. Works with all routers 3-1/4 HP or less. 120V, 20AMP. Give your router a feature only available on routers costing hundreds of Dollars. Easy to use-Simply plug in speed control and plug your router into the speed control turn dial slowly for best results. (Speed control has a clip that can be worn on your belt, hung on wall, or left loose). Using a speed control decreases tear out, stops burning, lets you feed at comfortable rate, provides better, safer results with large diameter panel raising bits, decreases wear on bits, makes less noise, and allows softer starts at lower speeds. A Dust Cover is included (not shown in photo). NOTE: Will not work with soft start or variable speed routers.