Motorcycle chain & sprocket set by JT Sprockets. A chain and sprocket set, as it is commonly called, includes the chain and the two sprockets (front and rear) that are necessary to transfer the movement from the engine (front sprocket) to the rear wheel (rear sprocket).

The front (small) gear of the set has 15 teeth while the rear (large) one has 39 teeth. This means that they have 15 and 39 teeth respectively on their perimeter. The pitch of the chain, which is 420, is the distance between its pins. This is indicated by the first digit of the above number, while the other two digits refer to the width and strength of the chain.