ACT 90-05 Mazda Miata XACT Flywheel Prolite (90-93 Must Use 1.8L Clutch)Dramatically improved engine response and acceleration, mild to moderate gear rattle; Heat treated forging for strength and toughness, induction hardened ring gears for maximum life; One piece construction allows less opportunity for failure and provides uniform efficient heat transfer from the clutch disc. No more warped inserts or loose ring gears; Recommended for race use; Forged, CNC machined and dynamically computer balanced for smooth high RPM