This important feature provides a variable natural frequency in the spring to help counteract damaging wheelhop. This is a feature of the OE springs often overlooked by other companies simply because they don't realize it's benefits in multi - purpose applications.BMR Suspensions SP009 lowering springs are available in red powdercoat for long - lasting good looks. Installation time is about 2 - 3 hours. Proudly made in the U.S.A.