I use them in my bobbin for piecing and machine quilting. The vendor told me you have to take out the spring in the bobbin case, if it has one, and then put in the washer. It's easy to take out and easy to put back in if you decide to. Picture here: http://www.premiersewing.com/bobbin-...in-case/spring. You can see a picture of the empty bobbin case with no spring and the washers here: http://www.daystyledesigns.com/magicgeniewashers.htm
The washers were designed by Sharon Schamber. They aren't expensive and last a long time.
These slick space age washers eliminate the backlash in the bobbin when changing directions at high speed. Backlash creates "birds nests" in free-motion quilting and embroidery. Just drop a LITTLE GENIE in the bobbin case, replace the bobbin and you're good to go!.
The Magic Bobbin Genie fits all domestic machines.
Designed by author, teacher and award winning quilter Sharon Schamber.