50 Pcs Premium Bobbins, The sewing bobbins are made of premium quality plastic, which is transparent and durable, could be reused many times with security notch for consistent bobbin thread winding. Standard size can be used on most sewing machine. Perfect for anyone just starting out with an embroidery machine or a sewing machine High quality transparent plastic sewing machine bobbins. Our bobbins are made of plastic, durable and practical, and the bobbin are smooth and will not scratch. If you any questions with our products, please do not hesitate to contact us!