Swift 40mm Soft Axle - Black Oxide 1040mm x 3.0mm - Universal KartingPrecision Flex for Optimal Grip When you demand maximum rear end compliance from your go karts supply, the Swift 40mm Soft Axle delivers the exact flex characteristics needed to keep your tires planted on low grip or rutted circuits. Engineered with a precise 3. 0mm wall thickness and spanning a standard 1040mm length, this driveline powerhouse is built to absorb harsh track vibrations that would otherwise break traction and cost you valuable tenths.