Readylift Rear Shock Extensions for the 1999-2014 Chevy/GMC Silverado and Sierra 1500 are constructed of tough powdercoated steel. The shock extensions will install in the factory upper rear shock mount and will help decrease the chances of over extending your factory shocks. Readylift 67-3809 is designed to work with your existing factory shocks with a 3" rear lift blocks. If you use your Chevy truck for off roading which can cause excessive rear suspension cycling, the stock rear shock may not be long enough.So instead of purchasing new shocks, the Readylift affordable Rear Shock Extensions are the perfect addition you can make for your truck!