Shimano SG-3S20-B is a three-speed hub with a set bolt type bell crank. It is designed for quick and precise cable adjustment and has an internal shifting mechanism with three optimum gear ratios for various traveling conditions. The hub is easy to operate and does not require any special ability or practice to shift gears. It is also compact and easy to maintain, with complicated mechanisms loaded in a cassette system. The SG-3S20-B is a versatile hub that can be used for a variety of riding conditions, from commuting to touring.