DT Swiss H 1900 Spline 30 Rear Wheel - 27.5" 12 x 148mm 6-Bolt Micro Spline BLKDT Swiss H 1900 Spline 30 Rear Wheel 27. 5" 12 x 148mm 6 Bolt Micro Spline Black. When motor assistance and leg power meet the range of terrain a bike can conquer grows almost exponentially. The H 1900 SPLINE is designed for this now upgraded with the famous DT Swiss Ratchet technology. The Ratchet LN system distributes the combined forces from the rider and the motor over a larger area than the previous pawl freehub systems increasing the systems