SRAM PG-950 9-Speed Road Cassette
You don't have to jump on the 10-speed bandwagon to get ultra-precise shifting from a lightweight, durable drivetrain. But if you're still running 9-speed, it definitely helps to have a quality, precision-engineered cassette handling the rear-end shifting chores. One like the SRAM PG-950, to be specific. It doles out buttery smooth, consistent cog-to-cog changes that will let you keep up with the 10-speed pack without dropping a chain or a lot of change.