The Mustang Steering Rack Stops & Clamps Kit is a required part for 2005-2014 Mustangs using ROUSH 20-Inch wheels. This steering rack kit properly spaces the wheels so that the larger front wheels don't hit the inner wheel wells. A Mustang using the 20-Inch wheels would require one Steering Rack Stops & Clamps Kit.For 2015+ Mustang Steering Rack Stop Kit, please reference part #421970.