This kit is for 3,500lbs round axle which axle beam dia 2-3/8" . /br/br 4 x 5-1/2" long U bolts, U bolts dia. 1/2". /br/br For 3" round axle, bolt length 5 1/2", 1/2" diameter, for 1 3/4" spring. /br/br This product is tested and rated for trailer use only. /br/br This product is tested and rated for trailer use only