These rear shocks improves handling of your Mustang. The rear shocks are designed to work as part of the ROUSH Mustang Suspension Kit (part #401296) to provide superior handling without sacrificing ride quality. The ROUSH Rear Shocks are sold in pairs (for both the left and right front).; This rear shock and every ROUSH suspension part, are extensively engineered and tested by ROUSH's own performance engineers to provide optimum performance for your vehicle.; ROUSH suspension parts developed over many hours on the race track, slalom, lane change, skid pad, and on a wide variety of different road surfaces to provide the best combination of ride and handling. One tool that the ROUSH engineers use in this development is the DIVAS Data Acquisition System, the same system used by Ford engineers for collecting and analyzing vehicle dynamics. Rather than simply providing the best quality suspension parts available, ROUSH takes its development a step further by finely tuning its suspension offerings to the specific application as part of a whole system. The benefit of this approach is that ROUSH suspension parts work seamlessly with the other dynamic aspects of your car.