•Made of quality steel material, with nickel-chromium treatment, high temperature resistance, corrosion resistance, no deformation, providing long-term durability •High precision teeth ensure close connection with bicycle hub for smooth rotation and easy maintenance •The hollow design reduces weight and makes your riding easier •Use it to directly replace your old or broken flywheel. Easy to install •A wonderful accessory for most road bike Specification: •Material: steel •Teeth ratio: •11-12-13-14-15-17-19-21-23-25T 247g (for road bikes) •11-12-13-15-17-19-21-23-25-30T 294g (for road bikes/folding bikes) •11-13-15-17-19-21-23-25-28-34T 366g (for road bikes/folding bikes) Package included: •1 x Cassette Flywheel