It's a direct-fit replacement piece for the low-roll-center suspension mounting system on this vehicle

This high-performance 7

HPI HPI86999 39T Ball Differential Bevel Gear

The product page confirms SKU PHB6443 and UPC 800185008675

Part number: PHB2400RX

Traxxas 10247-RED Servo Horn Aluminum Red Tires/Wheels It's a direct-fit replacement pieceAluminum steering servo horn with a red anodized finish. The servo horn is where all steering force leaves the servo, so it takes the highest concentrated load in the steering system. A composite horn flexes under that load and eventually strips at the spline, which loses steering entirely. Aluminum is the sensible upgrade once you fit a higher torque servo, since the extra torque goes straight through this part. Designed to work with the 10246 series