This disc is sprung centered for noise reduction on solid ACT flywheel. Must use ACT flywheel with sprung hub discs (flywheel not included). 4 Pad Sprung Race Disc Aggressive engagement, quick shifts, OE to mild gear rattle; Premium ceramic friction materials provide moderate wear rates and high heat tolerance; Utilizes wraparound spring windows, thicker retainer stampings and a heat-treated, spring steel drive plate to provide support, reduce stress concentrations and increase strength and reliability; Recommended for race use only; High burst strength and holds 28% more torque than typical organic materials 4214122 is a 4-pad spring-centered race disc made with high quality, ceramic friction materials. The engagement is harsher, but shifting is faster. 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. The race disc features a heat-treated spring steel drive plate and is well-suited for the smaller disc sizes in smaller engines.