Fil-Tec Magna-Glide Classic - Poly - Class M Bobbins - Cool Grey 3 - 10 count - The patented magnetic core creates consistent delivery throughout the entire bobbin. No more interruptions for tension adjustments as your bobbin gets smaller. The magnetic core prevents backlash or over spin, and eliminates the need for backlash springs. The magnetic core bobbin offers significantly more stitches per bobbin, reducing defects and increasing productivity. Fil-tec uses only the finest quality, high tenacity polyester yarns to make the magnetic core embroidery bobbin. Advanced EB cross-link technology reduces lint and residual build-up in the bobbin case and tension spring. The result is a more trouble free bobbin. Magna-Glide is the original high yield magnetic core bobbin.