BOX Two Prime 9 Cassette - 9-Speed 11-50t BlackPrime 9 Technology offers fewer gears with wider spacing to ease set up, provide a better chainline, and result in less wear and tear Ultra wide ratio with consistent progression Fits HG splined Shimano SRAM 8 10sp freehubs Box One features durable unibody construction with a lightweight internal support disc and black chrome plated protection Box Two features hardened steel cogs pinned to aluminum spiders and an ED black finish Box Three features