All KPMI valve springs are designed in house using sophisticated, proprietary design and simulation software programs. Their engineers, software, and 75 years of experience enable us to determine critical characteristics including stress, natural frequency, system harmonics, and fatigue life. Our spring manufacturing partners are U.S based companies that are ISO certified. The Super-Clean Chrome-Silicon valve spring wire we use is traceable back to Kobe Japan where some of the best spring wire in the world is manufactured. Each spring goes through a rigidly controlled heat treatment, stress relief, and shot peening process. Combining our design, simulation, and manufacturing protocols with this premium quality valve spring wire allows KPMI to supply you with the best possible valve springs period