A matching diameter does not establish watch crystal fit. Two round crystals can be the same width yet have different thicknesses, profiles or mounting requirements.
1. Identify the complete shape. Check whether it is flat or domed and whether its edge has a bevel or step. Ask for the exact replacement reference or a section drawing, not just a diameter.
2. Check the mounting specification. Sternkreuz’s crystal catalogue separates thicknesses and profiles, including designs with different gasket forms. Match the crystal and specified gasket to the case’s seating design; a similar-looking ring is not confirmation.
3. Confirm the assembled result. Before wearing the watch, have the installed crystal’s seating and hand clearance checked. If water resistance matters, the finished assembly needs appropriate pressure testing. A new crystal alone proves neither fit nor sealing.
Watcher Insight: use the complete compatibility checklist to check the crystal alongside the chapter ring and hand stack.
