Longines Factory Mainspring for caliber 5/16N - Steel

Longines Factory Mainspring for caliber 5/16N plus perhaps similar ébauche watches, steel, new in open envelope. The wonderful thing about factory mainsprings is they always fit! I likely have several of these so the one you get may differ slightly from the images. 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.