Filament Polyester . Fil-Tec Bobbincentral's patented magnetic core creates consistent delivery through the entire bobbin. No more interruptions for tension adjustments as your bobbin gets smaller. Magnetic core prevents backlash or over-spin and eliminates the need for backlash springs. Magna-Glide is the original high-yield magnetic-core bobbins. These are Style M Bobbins. There are 10 Per pack

• Color: Gray
• Recommended Needle Size: 65/9, 4.0 Longarm
• Made of: Polyester
• Recommended Use: Bobbin thread
• Thread Weight: 40wt, 2 ply
• Length: 132yd