As can be seen in the pictures, the rotor is solid. On the Wilwood site it shows drilled & slots (?).
Mine may be an older kit ? Has 10.75 as the measurement.
It should have been 11.25 to fit the pads properly though.
As can be seen in the pictures below, there is room under the rotor for that size.
So. In my opinion, better engineering should have been done.
I will not buy these again.....