This is a bobbin to fit machines that use Brother SA156 bobbins, AKA size 11.5. It's 20mm in diameter and 11.5mm of spool space in the middle. The ends are ever so slightly thicker than OEM, but I've tested with my Brother CS6000i machine and it works fine, both winding and sewing. Used a bit of superglue to attach the two pieces together. Pics comparing OEM with printed included!
I did a bit of filing to smooth out the edges after printing to make sure thread wouldn't snag.