The new DEORE XT M8100 series includes innovative features such as the MICRO SPLINE cassette with 10-45T or 10-51T gearing, HOLLOWTECH II crankset in 1x12 or 2x12, powerful 2-piston and 4-piston brakes, adjustable ISPEC-EV shifters, precision-tuned 12-speed rear derailleur and front derailleur, ICE TECHNOLOGIES FREEZA rapid-cooling rotors and complete wheelsets for XC or Enduro, all tuned to the needs of today's mountain bikers. SHADOW RD+, Silent drivetrain to minimize distractions Rear derailleur stabilizer reduces chain click Simple solution for chain drop Lighter and more efficient than roller-type chain breaker. HYPERGLIDE+, The new HYPERGLIDE+ drivetrain chain and cassette design propels the next generation of MTB riding by improving speed, shifting efficiency, and fluidity on any terrain. Benefits and features: Improved chain engagement, improved retention, and smoother pedaling deliver more power and confidence on sharply changing terrain. Definitive downshifting and upshifting in both directions encourages rider focus and acceleration. The ultra-efficient drivetrain with smoother, powerful transmission improves comfort and reduces rider stress. A wide range of gearing and cassette options, along with a single or double front chainring, cater to a wide variety of MTB riding preferences, abilities, and styles. HYPERGLIDE+ will help propel the next generation of mountain bike riding by introducing seamless pedaling on virtually any terrain. This revamped drive system and exclusive chain deliver rapid shifting, efficient power transfer, and unparalleled chain stabilization. Details: B-Axle Hollow Shaft Compatible Chain: HG 12-speed Direct Drive (Conventional) Fluorine Coated Link Bearings: 4 Lower Sprocket Max: 51T Lower Sprocket Min: 45T Max Front Diff: 0T Pulley Pulley Bearing G: Sealed Bearing Pulley Sunken Type Pulley Pin Pulley Teeth: 13T Pulley Pulley Bearing T: Sealed Bearing Pulley Housing: SGS Rear Speeds: 12 Top-Normal Spring Type: SHADOW RD+ Top Sprocket Max: 10T Top Sprocket Min: 10T Total Capacity: 41T