Strengthen your stock I.R.S. trailing arms with this box and gusset set. Six pre-cut steel pieces weld to the inside back, top and bottom of the stock I.R.S. rear trailing arms greatly improving strength and rigidity. An economical alternative to custom fabricated trailing arms. Not compatible with stock shock mounts. Welding required. I.R.S. Box Kit, 6 pcs., Raw 60-1964