Shimano lx rear derailleur rapid rise m580this shimano lx m580 rear derailleur shifts cleanly and reliably and features rapid rise technology this technology works in the opposite way to standard rear derailleurs resulting in quicker shifts through the cassette its compatible with all shimano 9 speed shifters but is best used along with shimanos rapidfire shifters features proven shimano precision shifting smooth operation mega9 compatible for use with 9 speed drivetrains top normal spring