FilTec MagnaGlide Classic Prewound Bobbins LStyle 67x2 HighTenacity Polyester Filament No. 60 Tex 12. The 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 overspin and eliminates the need for backlash springs. MagnaGlide is the original highyield magneticcore bobbin. 100 White bobbins per box135 yards per bobbin.