Shimano FH-M900 is a high-quality freehub and cassette sprocket system designed for mountain bikes. It features a Hyperglide 8-piece sprocket set with a wide range of gear ratios for efficient climbing and descending. The system is compatible with narrow type HG chains and requires a frame with an over lock nut dimension of 135mm. The FH-M900 also utilizes a dust cap to protect the internal components from dirt and debris, ensuring smooth and reliable shifting performance.