One of the most common causes of rear end component failure can be traced to the stock rear end caps. To cure this problem MW makes a replacement cap from billet steel with an increased cross section and heat treated grade 8 hardware (included). Requires precision measuring of the cap bore and milling of cap parting line to install. Normally, only the driver’s side cap has to be replaced, but most customers replace both. Check out the cap installation instructions (Service Bulletin #0007). Not a returnable part after it is installed.