Bobbin Case NB1275000 Drop-in bobbin case for top-loading bobbins. Fits Singer models 3709, 3722, 3810, 3820, 3825, 6510, 7312, 7322, 7350, and 7380. Fits Viking models Husky Star C10, and Husky Star C20. Fits White model 3100. Fits Pfaff model Smart 200C.