Beach RC says... 

Upgrade your Team Associated race kits with the NEW FT Aluminum Rear Hubs. Available in anodized blue or black aluminum with laser-etched FT logo, these hubs add an extra level of bling and precision to your rides. With two set screws to further secure the hub and hub insert to the hinge pin, you can be sure these hubs will stay consistent run after run.

• Available in both blue and black anodized aluminum for increased durability and precision
• Set screws included to ensure a play-free assembly
• Fits: RC10B6.2, RC10B6.2D, RC10B6.3, RC10B6.3D. Use #91877 (blue) or #91878 (black) as a direct replacement for #91857 RC10B6.2 Rear Hubs
• Hub weight: 10.3g ea