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.