Center and Off Center is in reference to the roof.
We will contact you for exact location.
Patent Pending adapter matches the contour of the OEM roof so the Maxxair Dome mounts to a flat surface. Prevents distorting the roof sheet metal or vent flange and can be used as an aid for locating the fan. They are CNC machined out of UV and fire resistant expanded PVC. The fan mounts to the outside adapter. The adapter ID is 7" and the OD is 10.5"
If you have questions about this product you can call Hein at 541-49O-5O98