Hi i have bought Spec flywheel and clutch (stage 2)..
Can anyone tell me if this flange is needed.
They are none on the original.
That is a shim that goes under the slave cylinder, Depending on which clutch you are installing, you may need to shim the slave to prevent over-extending the slave which will blow-out the seals.
From from what I've seen most aftermarket clutches require shimming, I know some people don't use a shim and have no issues,, I wasn't one, for my ACT clutch I need to use a .06" (1.5mm) shim, ..
Here's my rather simplistic way to figure if you need to shim,
One, measure the FW thickness of both the OEM and the Spec,
Next, install the clutch on the FW and torque them down to ensure the PP fingers are at their installed height .. While resting on that flat surface, measure the finger height of both clutches and then shim up any difference between ...
Here's RAM's tech write up of determining the slave preload, Factory Hyd. setup
Good luck ..