Rear wheel axle for big ball-bearings produced from world-renowned HUDY Spring Steel™. Strategically machined for toughness and light-weight without compromising power. The wheel axle is likewise hand ground for maximum accuracy to ensure a great, accurate easily fit into suspension system ball-bearings, guaranteeing perfect wobble-free fit and rotation. Heat addressed for optimum power, durability, minimal wear, and extra-long lifespan. Fits just multi-adjustable back upright #323355.