Spread the load Z blocks and other axle spacers used by Hendrickson, Freightliner, Kenworth, Mack, Hollis, Sterling, Ford and others create pressure points that will crush or even break the toughest of caster wedges. Use this HD Wedge Spacer Plate tospread the load and then use the caster shim of your choice to modify alignment. The 18 thick plate comes 6 to a pack and provides support for 4 wide axle spacers. The HD Wedge Spacer Plate can also be used to dial in ride height from side to side. California Residents WARNING