SS and G6 discs are Sprung Centered for noise reduction on solid ACT Flywheel. Must use ACT Flywheel with Sprung Hub Discs for proper clearance. (Flywheel not included) 6 Pad Sprung Race Disc Aggressive engagement, quick shifts, mild to moderate 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 high horsepower street or race use; High burst strength and holds 28% more torque than typical organic materials 6250623 is a 6-pad spring-centered race discs 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 6-pad, spring-centered disc is recommended for larger clutch sizes to absorb more heat and for smoother engagement.