First of all, they have aluminum top and top has got a stamping on there indicating if it is for a speed control or if it is for lighting as a dimmer control. Now the dimmer control also has some fingers on there and those fingers are the total wattage used as far as the total wattage in the light fixture or the room that you are actually dimming as far as controlling lights.

Now light bulbs come in a lot of different shapes and sizes and wattages. If you are going to need to control a chandelier for an example, you want to always take the maximum light bulb size and multiply it by the number of light bulbs in the chandelier. For an example, six bulbs, maximum 60 watts, 360 watts. So therefore you do not want to buy a 300 watt dimmer switch. Because if you do, it will burn out very quickly, so you want the next size which would be in this case a 500 watt unit. A 500 watt will control very nicely unless you are to add more bulbs or more lighting in the room. That way you would have to compensate and possibly buy even a larger dimmer switch.

So there you have it folks. It is a very important to have the right unit for the right job.