MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
1 inch = 25.4 mm
So the default clips have roughly the following clamping widths:
You have to consider, though, how the units are used by your slicer and printer. STL files don't declare units, so if your slicer defaults to inches, it might think that the 120 mm clip is in fact a 120" clip!
If that's the case, you have to scale down the object in all axes by a factor of 25.4, or to 3.937%, to get back to the original size. (Since a bag clip is not a precision instrument, you could go with 25 or 4%, and get a perfectly adequate clip too.)
I hope that helps ... let me know how it works out! :-)