PKT 40mm Axle 3.2mm Thick for Robust Track StabilityWe built this PKT 40mm axle with a 3. 2mm thick wall for serious stiffness.. exactly what you need for more grip on sprint racing courses. The extra wall thickness makes the axle noticeably stiffer than the thinner versions. This helps plant the rear tires better under power and through tight technical sections. Less flex = better traction and more consistent lap times on sprint tracks. Stick with our PKT keys.. youll need four PKTAK8 keys (sold