Amecotex&reg; - 144-Pack 75D/2 Cardboard Polyester Prewound Style ''L'' SA155 Threads Sewing Embroidery Bobbins 3/8" x 13/16" (Black) 144 Prewound Bobbins. Size "L", SA155 Cardboard sided provides uniform tension. High yield fiber equals more stitches per bobbin It is wound on a cardboard sided bobbin shell. Because of this, it is not affected by humidity or oils. It is responsive to machine thread sensors so you dont have to worry about your yardage. 100% Polyester Filament Bobbin Thread, Style ''L'' SA155 Bobbins will fit most commercial embroidery machines and many home embroidery machines. You can see the comparison chart at www dot allthreads dot cn/25/bobbin-comparison-chart.html