Includes Monoloc. HD-M/Race Rigid 4 Pad Light to moderate pedal effort, aggressive engagement, increased gear rattle, confidence during hard shifts; Moderate friction life, extended by ACT's exclusive diaphragm design, dramatic improvement in release mechanism life, rigid design may increase spline wear; Carefully engineered, precisely assembled, accurately balanced, uses select ceramic friction materials for high heat tolerance and maximum performance, major improvement in release mechanism; Recommended for race use only; 100% clamp load tested and dynamically computer balanced for smooth high RPM reliability, includes ACT's patented Monoloc SB9-HDR4 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'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. Monoloc is a one-piece, direct replacement or upgrade to the standard, two-piece wedge collar and wire ring featured in pull-type clutches. The spring tension of the segmented retaining ring is carefully calculated and tested for optimal performance. It provides uniform loading on the bearing and pressure plate to assure proper alignment, regardless of driver influence or vehicle modifications. Monoloc's hardened chrome-moly steel construction will provide years of service.