NuVigor Mainspring No. 20½ for Bulova 4AT & 4FL, Gruen & Benrus - Steel

NuVigor No. 20½ steel mainspring for Bulova caliber 4AT & 4FL, Gruen 307, 327, 328, 329 and Benrus 4½ ligne movements, and quite likely others. Steel, new in envelope. See images for 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.