Radius Upgrade Kit - EXP 3.0 To 4.0. Do you have a RadiusX 3.0 or RadiusCX 3.0 auto-clutch system in your bike? This is the EXP 4.0 upgrade kit for you! Quickly and easily upgrade your existing auto-clutch system to enjoy the benefits of Rekluse's next-generation auto-clutch technology: EXP 4.0. This upgrade includes a redesigned EXP 4.0 disk fully assembled with Rekluse's recommended tuning settings. Replace your EXP 3.0 disk with your new EXP 4.0 disk and you're ready to ride! What's Included: Assembled EXP Disk: Consists of: EXP Bases, Rolling Wedges, EXP Springs, Quarter Turn Pins. Why Upgrade to EXP 4.0: More direct power delivery, improved durability, and rider-focused functionality. Upgraded base material providing improved strength at high temperatures.