For removable and top dropin 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, HusqvarnaViking, JanomeNew 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.