JP4 - HDSS kit features ACT's highly regarded Heavy Duty pressure plate and most popular street disc delivering generous torque capacity, smooth precise feel, quiet operation and increased toughness to withstand the rigors of spirited street and off - road use. ACTs exclusive diaphragm design increases clamp load, reduces deflection and maximizes clutch life. All diaphragms endure a four - stage heat - treating process for unparalleled performance. ACT precision pressure plate cover stampings provide rigidity and consistency while precision machined pressure plate castings absorb heat. ACTs performance street discs boast quality parts throughout with robust center sections, premium organic friction materials for exceptional wear and improved heat capacity which are steel - backed for greater burst strength and durability.