Currently, there are numerous string manufacturers in China, and the quality has improved considerably compared to the past. One of them, Huayin (Fine), is a manufacturer that produces strings for various instruments. Their DOUBLE BASS STRING for double bass is particularly known as a hidden standard string by those in the know. I heard it could be used for upright bass, electric upright bass, and silent bass, so I bought it as a spare, but I never used it and have been storing it at home. Therefore, it is new and unused. The strings are individually packaged to prevent them from being exposed to air, so I believe there is no deterioration, corrosion, or discoloration. Shipping will be on days other than Tuesdays and Thursdays.