JoAnns or Walmart are selling what they believe are original manufacturer parts. The specs are off and they do not work in my Singer 66 treadle. They caused tension problems that were resolved by switching to old bobbins. The made in China class 15 also are a not the best for vintage machines. They are difficult to slip onto the bobbin winder. I found a new in the package made in the USA old stock at a thrift store.