You can adjust the tension of the thread by turning the white knob. You can unscrew the thing, and have plenty of room to put in a small heavy blob of metal (I found in DH's shop) It doesn't wobble or tip anywhere now. I put a plastic straw over the spindle to make it longer so my spool doesn't dance off. The little fine tuning made it must have item for me. My grand winds dozens of bobbins, I'll never be bobbin poor. :D