Signature Series Valve Springs are manufactured using high-tech, super-clean chrome silicon alloy materials that are held to tighter stress relief and shot peen tolerances, making them stronger and more efficient than others on the market. A micro-peening process is used to increase durability and longevity of the spring, which means you can push harder for longer. In addition, the added heat treatment reduces load loss during operation. Some springs in the series are also nitrided for racers who are looking to increase lift capacity and number of cycles over the life of a spring. The Signature Series Valve Springs are perfect for extreme stress applications such as professional drag and oval track racing.