Fits '04 & '06 on the left rear Hyper 600cc Chassis. Our torsion arms are machined from 2024 Aluminum for superior strength. Rear torsion arms are measured from the center of the splined torsion bar hole to the center of the shackle mount hole. Squeeze bolt is included. Send us your old torsion arms or a sketch and we will offset torsion arms to your specifications at no charge.