Electro Mainspring for 3L Longines caliber 4.21 - Steel

JAR Electro steel mainspring "No. 1" for 3 ligne Longines caliber 4.21 and perhaps other wrist watches, new in envelope. See images for precise mainspring specifications. I specialize is 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.