Cognito forged steel Torsion Bar Adjuster Key Kit for 2001-2010 Chevrolet and GMC 1500HD / 2500 / 2500HD / 3500 / 3500HD 2WD/4WD trucks, 2001-2013 2500 2WD/4WD SUVs and 2003-2009 Hummer H2 and H2 SUTs. Torsion bar keys are used to set the ride height of the front of the truck and are commonly used in leveling kits, and it is important to set the height appropriately as to leave ample suspension droop travel to maintain a good ride quality. There are several different torsion bar spring rates that GM made and put in these trucks, the rate depending on the model and features of the truck. Some trucks that have a higher spring rate may not need aftermarket torsion bar adjuster keys to obtain the maximum recommended ride height. This kit is only used in leveling kit applications as well as lifted applications when the higher setting of that particular lift kit range is desired like taking a 4" Cognito lift kit to the 6" setting.