NuREZISTA Mainspring #654 for 22/0s Hamilton Facrtory No. 6621 - Steel

NuREZISTA Mainspring #654 for 22/0s Hamilton Movements, Factory No. 6621, steel, T.B. end, new in replacement envelope. The original envelope was so bad I replaced it. See image for precise characteristics. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.