Transparent plastic bobbins for Singer Class 66 systems, supplied in a tidy reusable storage box. Designed to deliver smooth, even winding and consistent thread feed in compatible models, they’re easy to identify at a glance. Use only the bobbin type recommended by your machine to protect timing and tension. Handy 12‑pack keeps backups ready for complex or multi‑colour projects. For best results, test on a scrap first and match tools to fabric weight and machine class for consistent results.