For removable and top drop-in bobbin cases. Consult your sewing manual to determine type of bobbin needed for your machine. Fits all Singer Class 66 models and some of the following machines: Baby Lock, Brother, Riccar, Simplicity and White. Bobbins not compatible with the following machines: Bernina. Elna, Husqvarna/Viking, Janome/New Home and Pfaff. Use only the same type (metal or plastic) of bobbin that came with your machine. 4ct per pack. 6 packs per box.