4" - 6.5" Rear Block Kits for 2017-2024+ Ford Super Duty F250/F350/F450 4WD OEM style fabricated steel construction flat or tapered block with bump stop landing pads, drive line spacer and new longer U-bolts For use with trucks with 1 or 2-piece drive shafts. Please Check to see if your truck has a 1 or 2 piece underneath. not sure? send us pictures.