When designing a rail vehicle, it is essential to consider factors such as loads, speeds, torques and installation space. These factors must be considered also when selecting the power transmission components. Bearings for gearboxes operate at high speeds and under high loads. They must be able to withstand shocks, vibration and extreme temperatures. Bearings for traction motors are required to have long service life. The most commonly used bearing types in rail vehicle gearboxes are cylindrical roller bearings, tapered roller bearings, angular contact ball bearings, four point contact ball bearings and deep groove ball bearings. In traction motors, most typical are cylindrical roller bearings and deep groove ball bearings. Often these bearing types are electrically insulated, with a corresponding coating on the outer or inner ring. For particularly demanding applications, hybrid variants are available. The rolling elements of hybrid bearings are made from heavy duty silicon nitride (Si3N4), an extremely hard wearing ceramic. Bearings for gearboxes and traction motors can also be customized and produced to special specifications, for example higher thermal resistance or more stringent tolerance ranges.