Prothane Coil Spring Inserts are available in five heights, so stacking is a practice of the past. These inserts prevent suspension bottoming and add a progressive compression rate to coil springs. Dampening inserts, when installed should be from 1 to 3 inches less in height than the springs installed height on Chevy vehicles, 3/4'' to 1-1/2'' less for Dodge vehicles, and 2'' to 3'' less for Ford vehicles. Specially formulated non-rebound polyurethane inserts offer yet another aspect to your suspension tuning by eliminating the amount of rebound after compression.