These "shims" are nothing more than flat washers. Add shims (all it normally takes is one per bumper bolt/wavy washer) between the wavy washer and bracket depending on which way you want the bumper to turn. Too far out at the top, like ours, calls for a shim in the bottom bumper bolt to angle the bumper in at the top. Add shims at the top bolts to angle the bumper out at the top. Never use shims between the bumper bracket and tail panel.