With a roller bearing we can create low fiction movement for a bearing block. Roller bearings are usually cylindrical in shape. On the other hand, ball bearings are spherical in shape and are used in a similar fashion to roller bearings. The dichotomy between both bearing types is in the contact surface between the rail and bearing. The contact surface for a ball bearing is usually a single point as long as the bearing is perfectly spherical and there is no deformation. Even if there is a little bit of deformation, there is only going to be a limited space between the rail and bearing. The effect of this is that the balls will have an inherent limit of strength. Unlike ball bearings, the contact surface for roller bearings is a whole contact line. This makes it very rigid and stable. It also enhances the system’s maximum load capacity.