Improve the ride quality of your lifted 2011-2012 Chevy Silverado/GMC Sierra HD with Firestone's new R4Tech system for the rear suspension. It's made for trucks that already have a front 6-inch lift. The R4Tech system replaces the factory leaf springs with SANLUIS Rassini's leaf springs with Firestone Airide air springs. The R4Tech system adjusts for varying load capacities, absorbing the road impact for passengers and cargo. The system includes an air compressor control system, but shocks are not included. MSRP: $2300.