Two sets of these are going to tie extensions off the diff mount into a reinforced area above on the chassis side. There will be double 1/4" wall section plates that gets clamped onto these big spacers which are 440C. The 5/8" bolts are titanium alloy. The countersunk washers are from an F-22, I'm guessing they're PH stainless. The material composition is not stated on the part number...
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