The Clear-Spun, Class 15 Pre-wound Bobbin from Fil-Tech holds 92-yards of high tenacity spun polyester thread. These pre-wound bobbins are recommended for most domestic machines and are available in two colors, black and white. The clear plastic on these bobbins works in conjunction with the thread sensors and consistently lets the sewist know when the thread is about to run out. Clear-Spun Prewound Bobbs are virtually lint-free and provide more stitches than your typical machine-wound bobbins. It also helps balance needle thread tension and offers high tensile strength, low elongation, and low shrinkage.