Features: 1.A special anti spin spring is built into the bobbin case assembly to prevent the bobbin from spinning when the machine is suddenly stopped. 2.If the bobbin spins when the machine stops, there is a good chance that a single loop of thread will fall out of the bobbin case. This condition will cause the thread to snap as soon as the operator begins to sew. 3.Bobbins can stop spinning more quickly, effectively preventing unraveling or tangling of bobbin thread when sewing operations stop and start. 4.The bobbin case is always applied as a replacement part for sewing machines, it can also be applied as a spare case. 5.Made of iron, durable and can be used for a long time. specification:Item Type: Sewing Machine Bobbin Case Material: Iron Size: 30x15mm Notes: 1. Manual measuring, please allow 1-3mm error,thank you. 2. Due to the difference between different monitors, the picture may not reflect the actual color of the item.e actual color of the item. PackageList:1 xBobbin Case