Enjoy the flexibility to switch between different thread and colors seamlessly with a set of four SINGER Class 66 Transparent Bobbins. These replacement plastic bobbins are a must-have addition to your sewing supplies, perfect for both novice and expert sewers. Class 66 bobbins are unique bobbins that are curved on the top and bottom and fit mostly older SINGER® machine models. Compatible with many SINGER sewing machines models including 247, 288, 360, 774, 935, 1022, 1280, 2210, 2517, 2732, 2950, 3270, 3343, 4325, 4610, 4622/22a, 4830, 5040, 5050, 5070, 5160, 5417, 5430, 5705, 5825, 5830, 5910, 6012, 6038, 6233, 7021, 8222, 8734, 9110, 9210, 9300, 9400, 9410, 9608, 9858, 57815, 57820, 57825, CG-500, CG-550, CG-590, HD110 and SR models 240, 250, 320, 340, 350, 400, 500, 700, 800, 1800, 2500, 3100, 3300, 4500, 5800, 6100, 6200, 6500, 6700, 8000, 9000, 9800. Please consult your machine’s manual to determine compatibility. In machine sewing, the bobbin thread forms the bottom part of your stitches, working with the top spool thread for strong, consistent stitches. Made from high-quality plastic, these bobbins ensure smooth thread winding and unwinding, preventing stitch irregularities and machine jamming. Using SINGER Bobbins is simple: wind your thread onto an empty bobbin, ensuring it is correctly seated in the bobbin winding tension disk of your machine. For best results, use bobbins that match the class/style of those that come with your machine and wind thread onto empty bobbins only, ensuring proper tension. Replace any bobbins that become chipped, bent, or damaged. Whether you're creating clothing, quilts, or DIY home décor, the pack of 4 SINGER Class 66 Transparent Bobbins delivers professional results with ease.