This allows BMR to offer a LIFETIME WARRANTY against spring sag.Blending aesthetics and performance, BMR has designed the SP067 for the handling crowd who uses their car on the road course or at the autocross. These springs will drop the rear of your S197 Mustang 1.5-inches and feature a fine-tuned spring rate to give you great handling. The 200 lb/inch dual-rate spring offers plenty of support, keeping the body flat and level in the corners. The lowered stance and increased spring rate decreases body roll and gives you a lower center of gravity for increased driver control in aggressive cornering situations. Combine this with BMR adjustable sway bars and you have the ultimate in handling and performance. When performance and looks are a must, rely on BMR's suspension!BMR rear springs retain the factory "hourglass" shape designed by Ford engineers. 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's suspensions SP067 lowering springs are available in red powdercoat for long-lasting good looks. Installation time is about 1-2 hours. Proudly made in the U.S.A.