Single mass lightweight chromoly flywheel. Made to fit the Valeo damped clutch for the ZF 6 gearbox (GS6-37BZ) from Z4, 130i etc.
see recommended articles. This flywheel weighs 6.3kg.
Balanced for motorsports and very suitable for high revs.
Fits all M50, M52, M54, S50 and S52 engines, as long as you use the ZF 6 gearbox.