Hello everyone,

I would like to change the FOIS sapphire crystal. Having looked around I found the below that could fit.
Could someone confirm how much work would be needed to get them to fit?

Previous models
- Hesalite with the black ring PN 063pw5139
- Hesalite with the silver ring PN 063pz5078

New models
- SPEEDMASTER '57 trilogy model Hesalite (does anyone know the part number?)
- Sapphire from the new 321 looks better in person than the FOIS sapphire (does anyone know the Part number?)

Thank you for the feedback!