This is a set of 4 of the cheapest double bass strings in the world, according to my husband. I don't know the details. He said he stopped putting on the E string because "something felt off..." Also, he stopped using them because there was a part that looked bent, as shown in the second photo. Even though they're the cheapest, they cost about 3,000 yen. Would you like to try them? No claims and no returns, please.