Product information updated on 2021-06-26 Manufactured by DJM Suspension - Part Number DJM:LB63LK, 1963-72 Chevy Rear Block Kit, Priced As Pair - Easy Install - Instructions - Yes. Allows adjustment from 3/8 inch to 1 and 1/8 inch drop in 3/8 inch increments. They fit in between the axle and trailing arms, think of them like adjustable lowering blocks. Longer U-bolts let you stack the shims to get your desired ride height! You can even fine tune out the “lean” that some trucks have! Complete with new U-bolts Commonly known as “Universal Lowering Blocks”, these babies will fit any truck with 2 ½” wide leaf springs. The cast aluminum blocks are made in 2”,3” and 4” flavors with the 4” blocks sporting a built in pinion correction angle. Of course, in order for them to work your axle must already be on top of the leaf spring. They are placed between your axle and the leaf spring and it lowers your truck by spacing your axle up towards the bottom of your truck. All Universal Lowering Block kits come complete with high strength U-bolts with rolled threads lock washers and nuts.