This is a optional Kyosho SP "Type B" Middle Suspension Arm Set, and is intended for use with the Kyosho RB5. These suspension arm set is from the KYOUM510 Factory Works Kit, and includes one front and one rear arm. The rear arms are are 2mm longer than the stock parts to improve steering. They also feature middle arm shock mounting holes, allowing you to replicate the Japanese Championship setup.
NOTE: These arms must be used with the KYOUM519-2 "Type B" rear hubs.