These Camburg leaf spring axle perches are CNC laser cut and formed to fit 3.5? OD axle tubing. They are 2.5? wide and 6? long for reduced axle wrap with the larger footprint for the leaf spring. The centering pin hole is 9/16?, depending on your leaf springs you may need to drill it slightly larger. These are a perfect complement to our Camburg rear end housing or for spring-under conversions. These are made in the USA and much stronger and higher quality than the cheaper stamped versions you see out there.