Micro relays are perfect for motorcycles where there is always a space and weight issue. Very rarely will you ever need more than 20amps (240watts @ 12 volts). Very often horns use more current than is wise to draw through the handle bar switch, especially if you use a louder snail horn or similar to make your presense on the road apparent to the seemingly psychopathic car drivers out to get you.Relays are very simple to use. Below is a very simple diagram showing how a relay is used to switch a lamp.What you are doing is to draw a very low current through your handle bar switch to power an elctromagnet which operates a much heavier switch to power the load. <<