Since I have more than one sewing machine, I use those silicone like round bobbin holders. I can get them at my LQS with a discount coupon. Nancy's Notions call them BobbinSavers. They don't break like plastic bobbin holders. In fact they can bounce a tiny bit. My bobbins are all plastic and each machine has a different size. I mark with a sharpie which machine the bobbins are for. I have one just for the embroidery bobbins to keep them separate from my sewing bobbins.