A sprocket is a wheel with the teeth, cogs, or even planetary gearbox Sprockets that mesh with the holes in the links of chain, track, or other perforated materials. A sprocket differs from a gear because a sprocket never 
meshes straight with another sprocket. Sprockets are designed to be used with a specific chain. Deciding on the best sprocket optimizes sprocket/chain conversation, ensures drive overall performance, and decreases maintenance.
