Moog offers two types of coil springs: constant-rate springs that restore handling to its original state, and cargo-coil, variable-rate springs as an upgrade for vehicles that carry heavy loads. Moog's constant-rate springs are built to replace original equipment springs, returning ride height and body sway to original performance levels. Replacing worn coil springs with Moog constant-rate springs restores vehicle handling. The cargo-coil, variable-rate springs change resistance as they compress and become progressively stiffer as the load increases. On both, Moog heat-treats the alloy steel to ensure the coils rebound fully and resist sagging. Moog also provides constant-rate springs with an enamel coating that resists corrosion and extends service life.