Super Twin Multi-Disc Clutch Kit, P-Trim, For BMW. Brandname: Spec Part Number: SB55PT Description. The Super Twin offers near-stock drivability, tremendous life expectancy, a no-shimming/setup bolt-in installation and maintenance free operation. Input Shaft Diameter: 1.390 in. Disc Diameter (in): 8.500 in. WARNING : This product can expose you to chemicals including Styrene, which is known to the State of California to cause cancer. The item "Spec SB55PT Super Twin Multi-Disc Clutch Kit, P-Trim, For BMW NEW" is in sale since Tuesday, March 9, 2021. This item is in the category "eBay ...