Pulled the invoice from my local dealer. I purchased the knob in September of 2014.
I bought a Z32 shift knob at the same time and the Z32 shift knob sits "lower" when compared to the B13 shift knob. Upon screwing down the Z32 knob. In order to make the knob not move and be fully threaded, the Z32 shift knob presses on the "boot skirt" or plastic ring that lays on the hump on the shifter itself. I did not want to modify anything and I want it to be OEM perfect so I used the new shift knob.
Sucks this item is no longer available.