Durst MG-Box 450 vs Femobox 450

Hi,
I have two boxes for Durst 1200 and they are slightly different.
Do anyone have any idea what are the difference between them?
Thanks a lot in advance

The exit pupil size of a normal color head is slightly bigger than a multigraph. The multigraph head has a build in shutter. The boxes are made accordly to the exit pupils.

Thanks for the answer.
Can I use both Indifferently on a VLS501?

Aside from a slightly less efficiency, yes. The MG-box will be ±0,3 stop slower.

Understood. Thanks