Made of high-quality metal, excellent quality, not easy to rust and rot, , can be replaced at will, smooth , never stuck. How to polish the bobbin case? Use ultra-fine sandpaper or use a soft cloth dipped in toothpaste to polish. You can also use hard , canvas and other materials to fold back the hard cymbals. What if the bottom thread of the bobbin is always wrapped around the bobbin case? There are two methods, first: slightly tighten the bobbin case of the bottom thread, and second: put a piece of paper inside the bobbin case, you need a pad until it does not shrink! How to install the bobbin: 1. First insert the lower thread and the upper thread into the sewing machine. 2. Pass the upper thread. 3. Pull the lower thread out of the needle hole. 4. Put the clothes to be sewn into the sewing groove and lower the pressure plate. 5. Start to pull the pulley and sew with the pedal. Features: 100% new and high quality. Reasonable size, light weight, easy to store and carry. Exquisite workmanship, smooth , no scratches. Easy to install and easy to use, it is an important part of the sewing machine. Weight: 62g Spool diameter: 2cm/0.8inch Bobbin thickness: 1cm/ 0.4inch colour: silver Material: metal Package Contents: 20 x spool 2 x spool box Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.