The Shimano MT401 Centre Lock Disc Mount 12 Speed 32H Q/R FreeHub uses Micro Spline technology to enable the use of a 10T cassette sprocket, to be used in conjunction with Shimano 12-speed cassettes. This freehub body with quick pawl engagement provides perfect traction and instant power transfer. Shimano redesigned their freehubs with Micro Spline technology for the arrival of their 12-speed cassettes. They maintain the width of existing freehubs but allow for the addition of a 10-speed cog to your 12-speed drivetrain. Micro Spline freehub bodies have 23 smaller and equally spaced saw-tooth angled splines to limit cog damage. This also results in a more even load distribution, enabling them to make their freehubs even more lightweight. Shimano MT401 Centre Lock Disc Mount 12 Speed 32H Q/R FreeHub Features Designed for use with Centre Lock disc rotors for secure hassle free setup Super quick engaging freehub body with pawl engagement giving near instant power transfer Modular industrial bearing construction produces a great value hub For Q/R fitment (Includes Quick Release)