Madeira Thread - Bobbinfil ThreadMadeira Thread - Bobbinfil Thread at discount prices! A fine, yet very strong bobbin thread made from 100% polyester. The weight of Bobbinfil has been specifically calculated to ensure compatibility with Madeira threads. Bobbinfil eliminates tension problems as all Madeira threads run with the same machine adjustments. Bobbinfil assists in the production of better machine embroidery.