Trac Dynamics Billet Series swingarms feature one piece CNC machined sides custom designed to give you great looks and superior strength! Extensive pocketing on the inside gets the weight down to a minimum making these arms only slightly heavier than conventional arms. Billet Series arms also include AXS (axle interchange system) axle adjusters that are made from super hard 7075-T7 aluminum. Their exclusive design allows you to change axle diameters in the future without having to purchase a whole new swingarm.