Clutch Springs are available in a variety of stiffnesses, and therefore different engagement RPM values. For more info, consult the spring vs. engagement speed diagram.
Red - 1400 RPM
Orange - 1800 RPM
Yellow - 2000 RPM
White - 2300 RPM
Black - 3000 RPM
Green - 1200 RPM
Clutch springs can be mixed with one another:
For example: Running two white springs and two black springs can be used, or other alternatives.
Each spring sold individually. Each Hilliard Inferno clutch requires 4 springs.