Standard size to fit most household sewing machines, such as Janome, Singer, Brother, etc. Made of PC material, which is different from PS, another transparent bobbin material on the market, the PC material is more durable and not fragile. At the same time, non-metal materials are not easy to rust and are smoother. Reusable: plastic sided prewound bobbin threads have clear plastic sides that will not distort or absorb machine oils. It also can be reloaded after empty. Sewing bobbin threads is daily sewing needs. Wide Application: It is a good helper when you sew clothes, it can also create a DIY work such as children's crafts, it will make your job simple and fun. Color: Transparent.The transparent bobbins let the color of the thread look brig.