Every AFCO Coil Spring is machine-ground on both ends to tolerances within 1 degree, and then pressed to solid height and "pre-set." This process virtually eliminates any potential for additional set. AFCO has made a science of optimizing the variables of material thickness and coil spacing to achieve the best possible design for each rate and height of spring in their product line. AFCOILS incorporate the use of super-high tensile strength chrome silicon wire for long life and and a consistent rate. All springs are cold wound on the latest automated coiling equipment and heat treated twice during manufacturing to be able to withstand even the most abusive conditions. To further enhance durability, AFCOILS are shot-peened and coated with a durable finish.