We are no longer providing our MS-1 on the e-commerce site. There were multiple strengths used in the original manufacture of SWCC movements, and multiple movement styles. Given the rarity of need to replace these springs, it doesn’t make sense to offer multiple versions on the e-commerce site.
However, if you think you need a new SWCC mainspring, please contact us and we will help you determine the best course of action based on your need and type of movement.