Magna-Glide White Continuous Filament Polyester Bobbins Size L. Magna-Glide pre-wound polyester thread bobbins are specifically-designed for metal bobbin cases used in commercial embroidery applications. The magnetic core offers uniform tension control throughout the entire spool preventing chances of thread breakage or bunching when sewing. Magna-Glide bobbins produce clean uniform stitches with little to no lint buildup and no overspin or backlash concerns, eliminating costly thread waste from lower quality bobbins with erratic tensions. Magna-Glide only uses premium polyester thread for their bobbins, making them a favorite for garment and embroidery businesses. Each box comes with 100 large sized bobbins and 135 yards of white polyester thread on an individual bobbin.