VARIABLE SPEED CONTROL, Add this to your 1/2hp MASTERCARVER® PRO-FLEX or other flexible shaft system or motor tool i.e. Dremel or Woodhogtm to vary the speed by dial control. This is a stand alone dial control. It varies speed up to maximum rpm of tool. Will also vary the heat of a 110V unregulated wood burning pen up to the maximum power of your pen. Note: it accepts pens up to 400 watts, will not increase pen's power. Simple connection, power cord just plugs in. Input voltage: 110V, max Amps 4.