HC4-XXR4 kit features a MaXX pressure plate for the serious enthusiast. ACT MaXX 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's 4-pad rigid race discs are made with high quality ceramic friction materials. The chrome-moly hub is heat-treated for strength and durability. The lightweight rigid design allows for quicker shifts and smooth trouble-free service. With the 4-pad rigid race disc engagement is harsher but shifting is faster. The 4-pad rigid race disc is well-suited for the smaller disc sizes in smaller engines.