Stock rubber flex discs allow for a slight amount of give, especially under heavy acceleration and, depending on the amount of force applied, could potentially tear or split. This slight flex/give can prevent instantaneous transfer of force to the wheels, making accelerations unpredictable, or even lead to your vehicle being stuck on the side of the track. To combat this, IRP's Performance Flex Disc was developed. Made of CNC machined aluminum, this flex disc won't actually flex, and the polyurethane bushings will only provide a enough give to dampen some vibrations and prevent damaging the transmission. This is perfect for high torque applications such a drag cars and dedicated track cars that want immediate response and long term reliability.

96mm Diameter

Fits the following BMWs:
2008+ E82 BMW 128i
5/1986-1991 E30 BMW 325e 325es M3 - Manual Transmission 
1987-1991 E30 BMW 325ix - Between Transmission & Transfer Case
1996-1998 E36 BMW 328i 328is 328ic - Manual Transmission only 
1999-2005 E46 BMW 323i 323ci 325i 325ci - Automatic & SMG Transmissions only 
1999-2005 E46 BMW 328i 328ci 330i 330ci - Manual, Auto, and SMG
2006+ E90 BMW 325i 328i 330i - Manual or Automatic Transmission 
2006+ E91 BMW 328i - Manual or Automatic Transmission 
2007+ E92 BMW 328i - Manual or Automatic Transmission 
2007+ E93 BMW 328 - Manual or Automatic Transmission 
1982-1983 E28 BMW 528e - Manual Transmission
5/1986-1988 E28 BMW 528e - Manual Transmission
1982-1988 E28 BMW 533i 535i 535is M5 - Manual Transmission 
1991-1995 E34 BMW 525i - Automatic Transmission
1989-6/1992 E34 BMW 525i - Manual Transmission
1993-1995 E34 BMW 530i - Manual or Automatic Transmission
1989-1993 E34 BMW 535i - Manual Transmission
2001-2003 E39 BMW 525i - Automatic Transmission
1997-2003 E39 BMW 528i 530i - Manual or Automatic Transmission 
1980-1989 E24 BMW 633csi 635csi M6 - Manual Transmission
2000-2006 E53 BMW X5 3.0i - for Rear Driveshaft
2000-2003 E53 BMW X5 4.4i X5 4.6is - for Rear Driveshaft
2007-2013 E70 BMW X5 3.0si X5 4.8i X5 xDrive30i X5 xDrive48i - for Rear Driveshaft 
1997-2002 Z3 BMW Z3 2.3 Z3 2.5i - Automatic Transmission 
1997-2002 Z3 BMW Z3 2.8 Z3 3.0i - Manual or Automatic Transmission 
2003-2008 Z4 BMW Z4 2.5i - Automatic or SMG Transmission
2003-2008 Z4 BMW Z4 3.0i Z4 3.0si 

This kit from Valeo is a simple way to easily convert your stock dual mass flywheel clutch system to a single mass system.

Dual mass flywheels allow for fluid-feeling clutch engagements and offer a more luxurious feel than single-mass flywheels. However, with these benefits come significant drawbacks. Why convert from a dual-mass flywheel to a single-mass flywheel?

Cost: Dual-mass flywheels are expensive, with the cost of replacement often times being double or triple than that of converting to a single-mass flywheel.
Serviceability: Single-mass flywheels can be resurfaced, eliminating the need to replace with the next clutch service. - something that is not recommended with dual-mass flywheels, as they contain a rubber section that is more failure-prone in high mileage application.
Simplicity: Single-mass flywheels lack the complexity of dual-mass flywheels, making them inherently more reliable. Dual-mass flywheels contain a rubber damper or hub that will, like all rubber components, wear out with time.
Pedal Feel: Many enthusiasts prefer to eliminate BMW's "Self Adjusting Clutch", which has been known to provide an unpredictable, inconsistent engagement point.
Driveability: Valeo's conversion kit has been designed to maintain nearly identical clutch and flywheel weight, ideal for keeping the clutch quiet and easy to drive.
Kit contents:

Single-mass flywheel
Non-Self Adjusting Clutch and pressure plate
Throw out bearing
Pressure plate bolts
Flywheel bolts
Clutch alignment tool

Since established in 2004, GSP North America has positioned itself as a leading supplier of New Axles in North America.GSP’s new axle program consistently offers the best application coverage, most SKU count, and more new numbers than any other competitors. GSP’s hub assembly program was introduced to North America market in 2010 and has grown into one the most trustable programs in US market.

This item fits the following BMWs: 

2008+ E82 BMW 128i 135i 135is 
2006-2011 E90 BMW 325i 328i 330i 335d 335i - Sedan 
2006-2012 E91 BMW 328i - Wagon 
2007-2013 E92 BMW 328i 335i 335is - Coupe 
2007-2013 E93 BMW 328i 335i M3 - Convertible 
2013+ E84 BMW X1 sDrive28i 
2009+ Z4 BMW Z4 sDrive28i Z4 sDrive30i Z4 sDrive35i Z4 sDrive35is