Specifications Hign-concerned Chemical:None Type:MTB Bike Freewheel is_customized:Yes Model Number:121146 Sensitivity:108 Sounds Flywheel Adjustable Gear Number:12 Material:STEEL Gear Teeth:12 Freewheel Speed:12 Origin:Mainland China Components:Freewheel SLR3 Ultimate 12 SPEED HG Cassette Compatible with mainstream 12 speed shifter. Mechanical kits are easier to adjust, electronic kits may require fine-tuning using advanced customization features. Material: Maximum 3 gear of 7075 high-strength aluminum + the rest of high-strength steel 11-46T about 282g 11-50T about 295g 11-51T about 297g HG HUB COMPATIBLE 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. Less than 299g ! The world's lightest mass-produced cassette challenge As a comparison M9101 376g ( 3 aluminum + 6 titanium + 3 steel) 11-46T=510%range XG1299 370g (1 aluminum + 11 steel ) XS1299 350g (3 aluminum + 9 steel ) 11-51T=520% range SLR Gen3 only 276g and 290g 11-46T=418% range 11-50T=455% range 11-51T=464% range