Pro - Series H - 11 Tool Steel 1.625 Triple Valve Springs Pro-Series H-11 springs are designed for the serious racer. Manufactured with the latest in laser technology. Each spring is manufactured using the most advance CNC winders in the industry. Each spring is parallel ground, stress relieved and deburred. They are then shot-peened and heat-treated to very specific standards. Inspected and batched to zero tolerance for the ultimate precision valve spring. This is the next generation tool steel spring!