Hi Jesper,

> My guess is that the volume is 8.363 cm3
> meaning that the weight will be about 85 grams.
> Could that be right?

Yep that's correct with the sizes you mentioned, because you didn't set the units, which I should of noticed also, the part exported out ten times bigger.

> I reckon this is why one half (bottom?) was not a solid.
> How do you see this, by the way?

When I first open a model from someone else the first thing I do is select it and in the information panel as shown below MoI tells me what the model is, in your case it was a joined surface.



Then to find out where surfaces/faces are not joined I use the script SelectNakedEdges http://kyticka.webzdarma.cz/3d/moi/#SelectNaked that's where I found that something wasn't right with the bottom half of your model, fixed it as mentioned above then exported it.

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