I thought I would bring up this old thread because I just learned about this product. My quilting buddy showed this to me last night. She bought a new machine and it has a horizontal bobbin vs the vertical bobbin in her Bernina. She has been having issues with stitching backwards. Now she is quite an accomplished quilter (wins at Houston) so it seems to be the new machine. She gave me one to try for my Viking D1. I've had the machine for two years now and just can't get the FM right with the machine. I'm anxious to give this little teflon washer a try.
I'm wondering a few things. Do these wear out? Why do they come 10 to a package? Is it because most people lose them? What about using these for regular sewing and for machine embroidery? I'm wondering if I can just drop it in the bobbin case and forget about it.