Generally
Gearbox that converts miles into kilometers, in an extra small version. Mounted between the gearbox and speedometer wire. Then the speedometer shows Kilometers instead of Miles. The gearbox contains a small gearbox with a gear set that shifts up the speed exactly by the difference between Miles and Km. ATTENTION! The protruding square pin that goes into the gear is extra long to fit many different speedometer gears. If it is too long, cut it to the correct length, otherwise it will lock the gear when you thread the nut.
