The old standard shims will not hold up to the extreme spring pressures and high RPM in today's race engines. COMP Cams offers a simple but effective solution to this problem. These Valve Spring Locators provide a thin hardened Steel alloy seat that will not only protect the head and shim but also locate and hold the spring in place. Previously this part has been available only in a cup form with the retaining portion being on the outside of the part. This required that the head be machined a great deal to accept this cup so COMP now offers an ID locator with the locating shoulder on the inside as well as the spring cup.