Pre‑wound bobbin thread for embroidery, sewing and quilting in a convenient reusable plastic bobbin. Sized for Singer Class 15 systems, each bobbin carries 45 m/50 yd of 50 wt 100% polyester for smooth stitches and fewer breaks. Set includes six black and six white bobbins to cover most projects. Reuse the bobbins by refilling to reduce waste and keep your kit organized. For best results, test on a scrap first and match tools to fabric weight and machine class for consistent results.