"Excellence in Performance", backed by the best one-year warranty in the industry! HD/Modified Street Light to moderate pedal effort, smooth positive engagement, OE to mild gear rattle; Longer friction life, extended by ACT's exclusive diaphragm design; Carefully engineered, precisely assembled, accurately balanced, with premium organic friction materials for heat tolerance and reduced fade; Recommended for street and occasional race use; 100% clamp load tested and dynamically computer balanced for smooth high RPM reliability 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.