I bought some and tried them, I was not impressed and never use them two machines with metal bobbins and metal springs. I have a vintage machine without a metal spring and tried the washer in it, works perfect without either one.

call the company who make them

Me either and I have close to 30 sewing machines! If one learns to adjust tension and use the machine properly, they're not necessary IMO.

Has anyone used them in a Singer 301? I wondered if they work in a side bobbin?

Thanks.

I use them for my FW and 301, Bernina, and Brother 1500. I like them because it stops the metal to metal contact which will cause static. A drop of Sewer's Aid will do the same thing though.

Doesn't the 1500 bobbin have a spring?

I took the spring out of the bobbin case. It's easy to put back in, if I don't lose it. LOL

i use a peice of thin paper with a drop of oil .....it helps the backlash

I thought I needed them, tried them and now they're in a drawer somewhere for my kids to find someday and wonder what in the world they are :)

I went the sewing machine shop in town and asked if she sold them. They told me they cause more problems and repairs than anything. I know Leah day swears by them but I haven't had a need yet. And the shop makes me weary.