Why use a prewound bobbins when you can wind your own? - A good question. The answer is that quality prewound bobbins are wound by high-tech machines which provide a smooth, uniform wind. The result is much more thread on the bobbin than a self-wound bobbin.
Whether you're in the middle of an embroidery design or a quilting or sewing project, having to stop to change the bobbin is always an inconvenience. Prewound bobbins are game changers for dedicated sewers and quilters. The convenience of popping in a new bobbin without spending time to wind it is worth every penny.
What does Class 15, L-style and M-style mean?
Class 15, L-style & M-style are the three most common sizes of prewound bobbins. Some longarm machines (A-1, Gammill, and Handi Quilter) take the M-style bobbin, which is larger in diameter than both L-style and Class bobbins.
L-style bobbins and Class 15 bobbins are nearly identical in diameter (Class 15 bobbins are about 0.5 millimeters larger in diameter).