www.dinanbmw.com will tell differences. stage 1 is springs and shocks, other stages offer that plus additional items. dinan has springs and other parts made to his spec. his bilsteins are revalved to his specs(sport bilsteins revalved softer). bottom line-- you can buy other systems cheaper, you can't buy his anywhere else. you first choice is whether to keep rear self-leveling. i've had his suspension 9 years... worth the price.