Trick Flow by PAC Racing Dual Valve Springs are manufactured to Trick Flow’s rigorous, world-class standards. Every spring is CNC coiled from high tensile-strength, extra-durable Pacaloy™ chrome-silicon steel and double shot-peened beyond Aerospace Material Specifications (AMS) reliability criteria. These dual PAC springs are specifically designed for cams with aggressive profiles, and are available with damper coils for extra spring surge prevention.