On an MH panelboard backbox, what does the B12 suffix designate on the catalog number? What does the T12 prefix indicate?

Issue:
B12 suffix in MH panelboard backbox and T12 prefix

Product Line:
PTFDS - FD Enclosure Systems

Environment:
Panelboard boxes sold and used in North America.

Cause:
Explanation for B12 suffix and T12 prefix on MH panelboard backbox catalog numbers.

Resolution:
The box has a 12`` bottom box extension. A T12 is for a 12`` top  box extension

Released for:Schneider Electric USA