Function: Derailleur (gearbox) is an important part of the bicycle transmission system, helping to convert the chain between gears on the rear wheel, allowing the driver to adjust speed and ability. transmission.Shimano SiS Technology: SiS stands for Shimano Indexed Shifting, which is an advanced shifting technology from Shimano. This technology uses a index mechanism to shift the chain between gears more precisely and smoothly.Performance and Precision: Shimano SiS provides high shifting efficiency and precision, allowing riders to adjust speed easily and smoothly.Applications and Uses: Shimano SiS derailleurs are commonly used on a variety of bicycles, from street racers to off-road and touring bikes. This technology is also integrated into many Shimano product lines, from high-end product lines to reasonably priced product lines.Service and Maintenance: To ensure smooth and efficient operation of the Shimano SiS Derailleur, regular service and maintenance is important. Proper adjustment and replacement of parts as needed will help maintain the best performance of your bike's drivetrain.