Utilizing a 14-Tooth / 14-Tooth pulley wheel combination, the SPRINT System is unmatched by any competitor on the market when it comes to strength, durability, and performance! ?The new midsize SPRINT System for Shimano Ultegra/Dura Ace 12sp is designed to only?work?with the 30T cassette and future smaller offerings (will NOT work with 34T cassette). ?All SLF Motion Systems use cages produced from "Made In The USA" 100% real carbon fiber (unlike competing brands' nylon plastic "composite" cages) along with unique coated bearings for added durability and performance. ?Improve your current stock drivetrain or even your current competing Oversize System with the installation of an SLF Motion System. ?Every System is designed, tested, and hand built in Pawnee, Illinois USA.