Why does the Weight of a part appear in BOM although its material is undefined?

I have a steel part that it's weight appears in the BOM despite that its material is undefined.

2 Answers

I think you have set up material properties density = 0.001000 g/mm^3
Check: Tools>Options>Document Properties>Material Properties>Density:
When is 0.000000 g/mm^3 your value in BOM should to be 0.00 g?
But for some reason the value goes back to the value 0.001 automatically, I don't know why.

My guess is that there's a default material in your properties setting. If you wish not to show the weight.. why not create a BOM without that field and use it? Otherwise, I would choose the correct material and let it output the weight.