The inner cables are not always directly visible on the bicycle, because they usually run inside a pressure-resistant outer casing. The outer casing protects the inner cable from dirt and water and thus also from premature wear. It also ensures that the inner cable does not slip during operation. The inner cables are necessary for brakes in order to transmit power from hand to brake, or to carry out shifting operations correctly. It should be noted, however, that there are different inner cables for brakes and gears and that they cannot be interchanged under any circumstances.