Shimano RD-T400 is a rear derailleur designed for 8-speed drivetrains. It features a total capacity of 43 teeth or less, making it suitable for a wide range of cassettes. The derailleur is compatible with sprockets ranging from 11T to 34T and can handle a front chainwheel tooth difference of up to 20T. It utilizes Shimano's Rapid Rise technology, which allows for quick and responsive shifting. The RD-T400 is designed to work with Shimano's SIS (Shimano Index System), ensuring precise and consistent gear changes.