EBC Brakes CSK Series Heavy Duty Clutch Spring Kits are approximately 10 to 15 percent stiffer than standard OE fitted springs and are sold in engine sets. They reduce the possibility of clutch slip and serve as an upgrade on OE fitted spring tension. EBC have developed these premium upgrade springs to replace tired or weak clutch springs, providing higher tension than standard springs without any real noticeable increase in lever weight. Clutch springs can weaken over time due to heat and abuse, which can result in premature clutch wear. Fitting upgraded springs is a worthwhile exercise when changing clutch plates. Note: Clutch springs should always be replaced as an engine set, not individually. In some cases, there may be 1 or 2 extra springs included.