The GPM STXM8039/1 is a hardened steel wheel joint developed for the Traxxas X-MAXX with measured improvements to structural thickness and pin diameter. The joint body is specified at 1.5mm thickness and the shaft pin diameter is increased by 0.5mm versus the original. Increasing the outer diameter from 17mm to 18mm provides improved rear power transfer and greater resistance to deformation under high torque loads, offering a robust upgrade path for performance-focused builders.