NA2 NSX-R Input Shaft

OEM Honda NSX-R input-shaft as used in the 2002-2005 NSX-R,

The twin splined main shaft accepts twin clutch plates allowing any NSX 6-speed transmission to accept widely available twin disc clutch kits for the 1991-1996 NSX that where equipped with the 5-speed transmission. 

Twin plate clutches lend them self's better to performance driving due to their relative low moment of inertia.

This results in the transmission being able to rev faster - allowing rapid rev-matched downshifts, hence why Honda used this design in the NSX-R.

This genuine part also allows 6-speed owners to use less expensive clutch/flywheel options from the 5-speed NSX.