The TeraFlex Z-Box is the perfect companion component to the Revolver Shackles. They are hinged to allow the box to open up to offer additional articulation and down travel to maximize traction and control. They also reduce spring stress by working in combination with the Revolver Shackles. Their opposing construction allows only one side to open at a time for added stability. The Z-Boxes help maintain proper driveshaft angles when used with the shackles.