The ReadyLIFT 6" Big Lift Kit is designed for the 2019-2021 Chevy Silverado and GMC Sierra 1500 trucks excluding Trail Boss ZR2 or AT4 / AT4X models. This kit with part number 44-39600 features advanced engineering for exceptional ride quality and handling. Its components include boxed steel front/rear cross members and a 3/16" thick steel front skid plate. The 1/4-inch steel differential drop brackets are double gusseted with a boxed center rib ensuring durability against torsional twisting of the front differential. The kit's standout feature is its heavy-duty angled and offset top mount strut extensions that realign struts for optimal shock performance and minimal wear. A lower mount strut pre-load spacer increases spring rate for handling larger wheels and tires. The rear lift comprises 5" tall fabricated steel blocks with integrated bump stop landings and Falcon 1.1 Monotube rear shocks. After extensive testing this kit is proven to enhance the ride of GM 1500 trucks. It allows for up to 35x12.50 tires on 20x9 wheels with 0 offset without trimming and larger sizes with modifications. However it's NOT compatible with Adaptive Ride Control Multimatic systems or trucks with rear composite mono-leaf springs (identifiable by round U-bolts); it works only with traditional steel leaf springs (square U-bolts). Key features include maintaining factory ride and handling top mount strut extensions for factory geometry 3/16-inch thick steel plate cross members and skid plate anti-torsion differential drop brackets fabricated steel rear lift blocks with bump stop landings Falcon 1.1 Monotube rear shocks and a ReadyGuard Powertrain Warranty. Note: Use of Auto 4 Hi is not recommended with this kit.