have you tried these and do they work?

I have, they work ok......Nothing spectacular

I have also tried them and they do seem to help if you are having bobbin problems. I have only used them on the front loading bobbin machines, not the top loading bobbins, although I am sure it would work on those, also.

One package should last forever unless you lose them all. They are pretty durable.

I use them on my Featherweight and high speed Brother. You have to take out the metal spring thing in the bobbin case. It's easy to put back in. It stops the static friction when the bobbin starts spinning that can cause birdnesting. I don't think the little disc does anything until I forget to put it back in the bobbin.

When I first got mine, I didn't think there was a big difference, however, after sewing for a bit without one in after a cleaning I noticed the difference. It helped a lot on my FMQ.

I don't know what or why you'd take anything out, it's just a flat nylon washer.

Yes, they do work, I have a top loading bobbin and it works fine there as well. The only birdnesting I've encountered was over where a lot of seams converged, and that wasn't a bobbin issue so much as a fabric-moving issue.

These also make great gifts to people with new machines!

What are Little Genie bobbin washers? Can they be used in any machine? Quilt Fan

Bobbin washers? I was not aware that bobbins got dirty. Or do they in time pick up a trace of chemicals from threads? And the chemicals build up till it does not turn smoothly?

The instructions say to take out the spring in the bobbin case or they won't make a difference. http://punchwithjudy.blogspot.com/20...n-washers.html