The Shimano 105 RD-R7100 is a 12-speed rear derailleur for road bikes using a hanger-mount setup. It is suited to riders building or replacing a Shimano 105 drivetrain and looking for a rear derailleur that matches 12-speed road shifting systems. The long cage design helps manage chain wrap for typical road drivetrain setups, and the black aluminum-alloy construction keeps the part lightweight and durable for everyday road use. This derailleur is intended for bikes compatible with Shimano 105 R7100-series 12-speed components and is supplied as the rear derailleur only.