Nivaflex Unbreakable Mainspring N4311 for Eterna 600, Gruen 153, Font 344, 8344 +many more - Alloy

Nivaflex Unbreakable mainspring N 4311 for Eterna 600, Font 344, 8344, Gruen 153, Langendorf 12, 722, MTS 321, 322, 327, 348, 356 and even more calibers plus perhaps other similar ébauche movements as well, alloy, new in envelope. See images for all supported calibers and precise mainspring specifications. 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.