Most rolling bearings consist of an inner ring and a outer ring, rolling elements (either balls or rollers) and a retainer (cage). The Cage separates the rolling elements at regular intervals holds them in place within the inner and the outer raceways, and allows them to rotate freely. Rolling elements come in two basic shapes: ball or rollers. Rollers come in four basic types: Cylindrical, Needle, Tapered and Spherical.Balls geometrically contact the raceway surfaces of the inner and outer rings at points, while the contact surface of rollers is a line contact.Theoretically, rolling bearings are so constructed as to allow the rolling elements to rotate orbitally while also rotating on their own axis at the same time.While the rolling elements and the bearing rings take any load applied to the bearings (at the contact point between the rolling elements and raceway surfaces), the case take no direct load. It only serves to hold the rolling element at equal distances from each other and prevent them from falling out.

Ball bearings are Classified according to their bearing ring configuration: Deep Groove, Angular Contact and Thrust Types. Rolling bearings on the other hand are classified according to the shape of the rollers: Cylindrical, Needle, Tapered and Spherical.

Rolling bearings come in many shapes and varieties, each with its own distinctive features.

However, when compared with sliding bearings, in rolling the starting friction coefficient is lower and only a little difference between this and the dynamic friction coefficient is produced. They are internationally standardized, inter- changeable and readily obtainable. Lubrication is easy and consumption is low.

When comparing ball and roller bearings of the same dimensions, ball bearings exhibit a lower frictional resistance and lower face run-out in rotation than roller bearings.

This makes them more suitable for use in applications which require high speed, high precision, low torque and low vibration. Conversely, roller bearings have a larger load carrying capacity which make them more suitable for applications requiring long life and endurance for heavy loads and shock loads.

Most of rolling bearings can carry both radial and axial loads at the same time.

Bearings with a contact angle of less than 45' have a much greater radial load capacity an classified as radial bearings. Bearings which have a contact angle over 45' have a greater axial load capacity and classified as thrust bearings. There are also bearings classified as complex bearings which combine the loading characteristics of both radial and thrust bearings.