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.