Trufit Mainspring - Hamilton 7221 for 8/0s movements - Steel

Trufit Mainspring - Hamilton 7221 for 8/0s movements, steel, new in envelope. B&C Trufit mainsprings were distributed by Barton & Chase of Philadelphia but made in Switzerland. See images for precise specifications. I specialize is hard to find watch parts and all watch parts are unconditionally guaranteed, even the cheap ones. Images do a pretty good job of representing the item.