NuREZISTA Mainspring #649 for 18/0s Hamilton No. 2721 - Steel

NuREZISTA  Mainspring #649 for 18/0s Hamilton Movements, Factory No. 2721, steel, new in envelope. See images for precise mainspring specifications. I specialize in hard to find watch parts and all watch parts are guaranteed. Images do a pretty good job of representing the item.