The component design of variable speed pulley of general bikes is too complex and it cannot float with chain parallel and easy to wear out causing failure. Mortop's pulley introduces the simple design concept, the overall simplification and the revision of pulley structure to make the pulley change to ideal angle by the lateral force of chain when speed changes and is able to keep horizontal floating with chain to reduce the wearing of these two parts to the minimum, which makes variable speed system faster and smooth- er. Mortop pulleys are uncomplicated designed with an integral amount of "float", or lateral movement. This movement allows the pulley to settle into an optimum position under each cassette cog. The result is faster, smoother shifts and a quieter drivetrain.