I checked, and the bobbin for my older viking is the same size as the 115 -though it has slightly rounded sides. I don't have a 115 up and running to see if it would work, but it fits into the case just fine. The 15 bobbins is quite a bit taller. Good to know all this, as I've ended up with three 115's. Now I've got to sort through my bobbin pile and see how many I have for the 115.