Swisscraft Mainspring No. 1311 for Gruen caliber 400 - Steel

Swisscraft Mainspring No. 1311 for Gruen caliber 400 plus perhaps similar ébauche watches as well, steel, new in envelope. See image for precise characteristics. I specialize in hard to find watch parts so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.