Kontronik FUN400/480's are both 28mm in diameter. The 480 is longer and heavier (110 vs 145g)
Either will work very well in the 480MF where the FUN400 is suited if you'd try to stay light and the FUN480 where you want all out performance. The FUN480-33 on 12 cells will be a total screamer.
FUN400-36 400W max (10cells)
FUN480-33 600W max (12cells)
Kontronik specs found at http://www.motor-mike.de/Kontronik/Index2.htm