The ultra lightweight steel flywheel (STU suffix) is recommended for forced induction and/or track and rally racing applications. This flywheel is machined with less material to assist in quicker revving capabilities. Well-suited for Stage 3 and up clutch applications. Stage 3 ? Street/Strip Series 2600 Clutch Kit This segmented Ceramic material with a performance pressure plate will provide the ultimate in street and strip combinations. This assembly is suited for up to 150% increase in torque capacity. Provides quick but smooth engagement and extended life. 300 mile break-in recommended with this set-up. The 2600 Series kit includes a performance pressure plate, a high torque sprung disc with segmented Ceramic facings,, all applicable bearings and the appropriate alignment tool. ULTRA LIGHT WEIGHT FLYWHEEL IS 17lbs