Fil-Tec’s patented magnetic-core creates consistent delivery throughout the entire bobbin. No more interruptions for tension adjustments as your bobbin gets smaller. Magnetic-core prevents backlash or over spin + eliminates the need for backlash springs. Magna-Glide Delights are produced using the top Glide colors, giving you a perfect match on the bottom & top of every piece you stitch. Fil-Tec uses only the finest quality, high tenacity polyester yarns to make the Magna-Glide patented magnetic-core bobbin. Advanced EB cross-link technology reduces lint & residual build-up in the bobbin case & tension spring. The result is a more trouble-free bobbin.