Rear wheel axle for large ball-bearings produced from world-renowned HUDY Spring Steel. Strategically machined for toughness and light-weight without compromising strength. The wheel axle is likewise hand ground for optimum precision to ensure a fantastic, accurate fit in suspension ball-bearings, guaranteeing perfect wobble-free fit and rotation. Heat treated for optimum power, durability, minimal use, and extra-long lifespan. Fits just multi-adjustable back upright #323355.