Single-stage flywheel, also known as single-chain wheel flywheel, is mainly composed of outer sleeve, flat block and core, jack, jack spring, washer, wire block, steel ball and other parts.

The chain, also known as vehicle chain and roller chain, is installed on the coupling wheel and flywheel. Its function is to transfer the pedal force from the crank and sprocket to the flywheel and rear wheel to drive the bicycle forward.