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 where radial projections engage a chain passing over it. It is distinguished from a gear in that sprockets should never be meshed together straight, and differs from a pulley in that sprockets have tooth and pulleys are smooth.
Sprockets are found in bicycles, motorcycles, vehicles, tracked vehicles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or even to 
impart linear motion to a monitor, tape etc. Probably the most common form of sprocket may be within the bicycle, where the pedal shaft bears a sizable sprocket-wheel, which drives a chain, which, in turn, drives a small sprocket on the axle of the trunk wheel. Early automobiles had been also largely powered by sprocket and chain system, a practice generally copied from bicycles.
Sprockets are of varied designs, a maximum of efficiency becoming claimed for every by its originator. Sprockets typically do not have a flange. Some sprockets used in combination with timing belts possess flanges to keep carefully the timing belt centered. Sprockets and chains are also utilized for power transmission in one shaft to another where slippage is not admissible, sprocket chains being used rather than belts or ropes and sprocket-wheels rather than pulleys. They may be run at high speed plus some kinds of chain are so built concerning be noiseless actually at high speed.