This Setup Spring is to use with the Nuke Performance 50mm Blow off Valve, to get the effect you want from your new Blow Off Valve is to use the correct setup for your current engine specification. We have three different springs to choose from, all designed for perfect fitment and performance in combination with our 50 mm Blow off Valve. Check the chart below to get to know which spring setup you should go with. Spring Pressure Chart : Engine Vacuum Reading = Color Code Between: 0,50 - 0,75 bar / 7,25 - 10,9 psi  : BLACK SPRING 0,35 - 0,50 bar / 5,07 - 7,25 psi : BLUE SPRING 0,00 - 0,35 bar / 0,00 - 5,07 psi : WHITE SPRING ** Measure engine vacuum at idle and with engine at operating temperature. Quantity : 1pc