Parted number not needed.
See my earlier post 9.9.2008 on locating MB Gear ****.

Removing..There are two section to the Xfire gear ****..At the bottom of the gear ****...Hold tight with one hand and with the other unscrew the very bottom section..may be a bit tight, but it will unscrew...DO NOT use grips or will damage base and then be unble to replace it in the future..

If you still having problems then enter "MB Gear ****" in Search for more help and suggestions..

Ken.

PS..Replacing with MB **** is easy. Its just a push on ..be gentle and take your time..