A sprocket[1] or sprocket-wheel[2] is a profiled wheel with tooth, or cogs,[3][4] that mesh with a chain, track or other perforated or indented material.[5][6] The name ‘sprocket’ applies generally to any wheel upon which radial chain sprocket projections engage a chain passing over it. It is distinguished from a gear in that sprockets should never be meshed together directly, and differs from a pulley for the reason that sprockets have the teeth and pulleys are clean.

Sprockets are used in bicycles, motorcycles, vehicles, tracked vehicles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear movement to a track, tape etc. Maybe the most common form of sprocket may be within the bicycle, where the pedal shaft carries a huge sprocket-wheel, which drives a chain, which, subsequently, drives a little sprocket on the axle of the rear wheel. Early automobiles were also largely powered by sprocket and chain mechanism, a practice largely copied from bicycles.

Sprockets are of various designs, no more than efficiency becoming claimed for every by the originator. Sprockets typically don’t have a flange. Some sprockets used in mixture with timing belts possess flanges to keep the timing belt centered. Sprockets and chains are also used for power transmission from one shaft to some other where slippage isn’t admissible, sprocket chains being used instead of belts or ropes and sprocket-wheels instead of pulleys. They may be operate at high speed plus some kinds of chain are so constructed as to be noiseless even at high speed.