American Automotive steel lift blocks are stronger than aluminum. They are designed to increase rear load and towing capacity. American blocks absorb noise and vibrations, and are tapered for perfect pinion alignment. American Automotive u bolts are manufactured for maximum clamp force and are guaranteed for life. Made of cold drawn certified 1541 carbon steel OEM factory material with grade 8 hardware, American u bolts embody extreme strength and maintain OEM handling characteristics. These square u bolts are engineered to clamp 2.5 inch wide leaf springs and are 12 inch extra-long measured from the bottom of the bend to the bottom of the threads. American u-bolts provide an even distribution of pressure to protect against premature spring failure and unwanted movement. Allowances need to be made for all overloads and aftermarket leafs. 5 inch thread can be cut down to fit many applications. Lift Block Specs: 5" Long x 2.5" Wide, 2" Tall with 9/16th Pin. U-Bolt Specs: Square, 12" Length x 2.5" Width x 9/16 Thread Pitch