ACT 09-13 BMW 135i / 09-13 335i XACT Flywheel ProMassBrand ACT Part Number 601030 Category Drivetrain Flywheels Condition Brand New Original Manufacturer Packaging Noticeably improved engine response and acceleration, OE to mild 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;