The progressive springs give the truck much more of a planted feel when going over pot holes and expansion joints. Before, my truck would "jump" to the side when hitting an expansion joint on the slightest curve, but the rebuilt shocks with flutter stack and new springs have reduced it dramatically. Wheel hop has been reduced to basically nothing as well. Geiser Bros front coil springs are $500 and the Deaver rear leaf springs go for about $1300. If you don't have an aftermarket rear bump stop kit, you'll also need the SDHQ factory bump stop strike pad replacement kit which will run another $200.