Don't pay over the odds for a bike speedometer, this has the same functions if not more then some of the £20 ones listed on amazon so grab yourself a superb deal on this. Fits all wheel sizes, adjustable in settings menu We include everything you need to get started straight away even the batteries :) As its wireless you don't need to install any wires, just clip the receiver on the fork, the magnet on the wheel spoke, and attach the main speedo to the handlebars and away you go - full instructions are included although you probably wont need them as its very easy to do :) Over 14 functions including current speed, average speed, max speed, relative speed, (mph + kmh) + more as shown below