Fits '04 & '06 Hyper 600cc Chassis on the left rear. 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 kit is included. Send us your old torsion arms or a sketch, and we will offset torsion arms to your specifications at no charge.