TS4-HDMM kit features ACT's most popular Heavy Duty pressure plate. ACT Heavy Duty pressure plates use exclusive diaphragm design to increase clamp load, reduce deflection and maximize clutch life. All diaphragms endure a four-stage, heat-treating process for unparalleled performance. ACT pressure plates have precision cover stampings to provide rigidity and consistency. ACT modified spring-centered street discs feature premium organic friction material with high copper content for better heat transfer and steel-backed lining for burst strength and durability. These discs are modified with reduced marcel for faster shift action to complement ACT pressure plates. the heavy duty torsional dampening springs are stronger, in most cases, than standard springs and are provided in the best sizes and spring rates to suit the application. Modified street discs provide smooth engagement and quiet operation, with increased strength and reliability.