Specifications Hign-concerned Chemical:None Use:Road Bicycles Material:Aluminum alloy Origin:Mainland China Ultimate 12 Speed XD Cassette Ultraight Freewheel For XD Hub Material:high strength steel+aluminum alloy Compatibility: mountain XD system Range& weight: 9-11-13-15-18-21-24-28-32-36-40-46T(282g10g) 9-11-13-15-18-21-24-28-32-36-42-50T(295g10g) 9-11-13-15-18-21-24-28-32-38-44-51T(295g10g) 10-12-14-16-18-21-24-28-32-36-40-46T(293g10g) 10-12-14-16-18-21-24-28-32-36-42-50T(298g10g) 10-12-14-16-18-21-24-28-32-39-44-51T(306g10g) XD Freehub Compatible Compatible with mainstream 12 speed shifter. Mechanical kits are easier to adjust, electronic kits may require fine-tuning using advanced customization features The material of high tensile steel and aluminum alloy made by the technology of quench-temper hardening, makes it more durable and has extreme resistance to abrasion. Gen3 - The latest tooth shape I would say this is the biggest upgrade ever, both in terms of smoothness and noise level. It is truly a comprehensive evolution to remain lightweight while still having excellent strength. Hollow design,steel+aluminum alloy combined,ultimate weight We adopted the hollow design to reduce the weight to some extent. Less than 299g ! The world's lightest mass-produced cassette challenge As a comparison M9101 376g ( 3 aluminum + 6 titanium + 3 steel) 10-51T=510%range XG1299 370g (1 aluminum + 11 steel ) XS1299 350g (3 aluminum + 9 steel ) 10-52T=520% range Super light weight!!! 9-46T=511% range 9-51T=566% range Ultralight Weight About 282g~298g More advanced structure Compared to the previous generation XD, this time we have significantly changed the internal structure to make it stronger, more durable and compact. 8 colors available