Springs are sold in sets of 4.
Approximate Engagements :
Green - 1000-1200 RPM
Red - 1200-1500 RPM
Orange - 1500-1800 RPM
Yellow - 2000-2300 RPM
White - 2300-2500 RPM
Black - 3000-3200 RPM
* Engagement speed is defined as the speed at which the shoes first touch the drum. (NOT LOCK UP SPEED)