Save time and save thread with Prewound Bobbins. The Fil-Tec Clear Glide Bobbins allows you to both monitor the amount of thread on your bobbin and ensure even winding throughout. The thread on these bobbins are a No. 60 filament polyester. The clear plastic bobbin and storage container protect your bobbin thread from oil and humidity, thereby maintaining its original quality and structure. Each pack contains eight pre-wound bobbins with 135 yards of thread. These Class 15/A bobbins are suitable for most domestic sewing machines. Fil-tec products are made in the USA.