U-Bolt Top Plate. These are designed with the standard 2.5" GM leaf spring in mind but will work great with a spring anywhere from 2.5" to 2.75" in width. These will fit an Axle of 2.5" to 4" in diameter. All of our U bolt plates have 3 spring pin location options. They are .375" HR P&O Steel plate and can work with .5625" (9/16) to .625" (5/8) U bolts, we recommend 5/8", why use a lighter piece of steel when you don't have to?