With its Beam Spider construction, the new Shimano Deore XT M8100 12-speed cassette shaves weight while increasing Shimano's MTB gearing range another gear. Using Shimano's new Micro Spline freehub body and Hyperglide+ tooth profile, these 10-45 and 10-51T cassettes deliver advanced shifting performance. Details: Definitive shifting performance New shift ramp designs provide the fastest, smoothest shifts by HYPERGLIDE+ Beam Spider Lighter and stiffer construction Reduces cassette inertia resulting in faster acceleration and increased chain security Micro Spline 10T lowest sprocket realized by new FREEHUB body construction Wide range and close step 12-speed drivetrain Specs: Cassette Cogs: 10-45t: 10-12-14-16-18-21-24-28-32-36-40-45 Cassette Cogs: 10-51t: 10-12-14-16-18-21-24-28-33-39-45-51 Compatible Chain: HG 12-SPEED Series: XT Generation: M8100 Number of Speeds: 12 Finish: Anodized Weight: 10-45t: 461 grams Weight: 10-51t: 470 grams