These traction bars where designed for the serious diesel truck puller. They are made from heavy d.o.m. tubing and feature 1.25'' threaded inserts. You have your choice between polyurethane bushings,hiem joints,or flex joints. Frame and axle brackets are made from 1/4" thick steel for strength. The frame brackets have the ability to be bolted to the frame with 5/8'' bolts. The axle brackets are weld on only for superior strength.