High performance is ensured when you repair or replace components using the best available and most appropriate parts for your vehicle. Shocks are an older design than struts, but both essentially serve the same function, which is to dampen or absorb motion and keep the vehicle firmly on the road. Boots, mounts, hardware and cartridges are useful for protecting assemblies and extending their wear. Options for some luxury cars and SUVs are air suspension systems, which replace more traditional spring constructions with bags of air that adjust to driving conditions.