This is a set of left and right outer/axle drive cups for your rear drive train which have both been modified with beefy steel rings by Turtle Racing. They replace HPI stock part# 8688. These cups are built to take the punishment from hard landings and high performance engines. This set only includes the outer cups or axle drive cups. It's recommended you run both the inner and outer cups for maximum strength. Outer cups are product code TUR0003. If you run HPi stock or heavy duty dog bones you will need to grind down the pins on each end to be slightly shorter.