Features: The kit includes a 10-speed cassette flywheel, a 104BCD 170mm crank set, a 10-speed chain, a shifter, a rear derailleur, a center shaft and a hanger extender. It can greatly improve the speed performance of mountain bikes, combining aerodynamics to reduce bike weight and increase riding speed. Made of high-quality steel and aluminum alloy, it is sturdy and has nice durability, high strength, wear-resistant and impact-resistant, not easy to rust. It can be used to modify your bike shifting system, perfect as a gift for family, friends, colleagues, cycling enthusiasts, etc. Easy to install and use, with nice compatibility, smooth running, make riding easier. Specifications: Material: Steel and Aluminum Alloy Flywheel: 10 Speed(11-13-16-20-24-28-32-36-42-50T) Crank Length: 170mm Chain Rings BCD: 104mm Package Size: 260 x 180 x 150mm/ 10.2 x 7.1 x 5.9in Package Weight: 2015g/ 4.4lb Packing List: 1 x 10-Speed Cassette Flywheel 1 x 104BCD 170mm Crank Set 1 x 10-Speed Chain 1 x Shifter 1 x Rear Derailleur 1 x Center Shaft 1 x Hanger Extender