That is a center one-way set designed to be properly used with any Tamiya TA-02 framework. Setting up a one-way product means that front tires aren't braked, which provides sharper acceleration and improved cornering.
• One-Way Shaft x1
• Bevel Gear & 16T Gear x1 each
• 730 Ball Bearings x2
• 6mm One-Way Bearing x1
• appropriate for Manta Ray (2018), Top Force (2017) and TA02 framework cars.