American Automotive Silverado Sierra 1500HD 2500HD 3500HD 1.5" Rear Lift Iron Blocks + 12.5" uBolt FITMENT: 2001 - 2010 Silverado Sierra 1500HD 2500HD 3500HD 8-LUG 4WD/2WD; Does not fit models with spring overloads CONTENTS: 2 solid US certified cast iron lift blocks with 4 OEM grade steel square bend u-bolts, hi-nuts and security spring washers. TECHNICAL NOTES: Install the tallest ends of tapered rear blocks to the rear of the vehicle; Retighten u-bolts after the first 500 miles BENEFITS: American Automotive solid cast iron lift blocks are stronger than aluminum and cast as a single, more stable construction than blocks with pressed pins. They are designed to increase rear load and towing capacity. American blocks absorb noise and vibrations, and are tapered for perfect pinion alignment. Made for maximum u bolt clamp force with an even distribution of pressure, American axle u bolts eliminate flexing and provide the strength to maintain original vehicle handling. NOTE: U bolt color may vary