Shimano SB-3S30 is a gear shifting system designed for bicycles with Shimano Inter-3 hubs. It allows for smooth and precise gear changes with minimal effort. The Revo-shift lever features an intuitive twist-to-shift mechanism, making it easy to change gears even while riding. The system also includes a bell crank and brake lever, providing convenient and integrated control over both shifting and braking. With its user-friendly design and reliable performance, the Shimano SB-3S30 is an excellent choice for riders seeking a hassle-free and efficient gear shifting experience.