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This is a high‑quality generic case back sapphire crystal for the Patek Philippe Nautilus reference 5726 (annual calendar moonphase watch), measuring 27.5mm (diameter) × 1.7mm (thickness) with a flat round profile. Made of synthetic sapphire glass (Mohs hardness 9), it offers exceptional scratch resistance and excellent optical clarity, serving as a direct substitute for a damaged or scratched original case back crystal.
Material: Synthetic sapphire (Mohs 9), highly scratch-resistant, resistant to daily wear.
Precision dimensions: 27.5mm diameter × 1.7mm thickness – designed for the case back opening of the Patek Philippe Nautilus 5726.
Profile: Flat round – completely flat surface for flush mounting into the metal case back frame.
Optical performance: Usually uncoated or with a simple AR coating (confirm with seller), ensuring clear visibility of the movement.
Q1: Do I need UV glue for installation?
A: Usually not. Case back crystals are press‑fitted with a rubber gasket, not glued. Follow the original construction (press‑fit + gasket).
Q2: Is this crystal made of sapphire?
A: Yes, this product is synthetic sapphire glass, Mohs hardness 9. If in doubt, ask the seller for material certification.
Q3: How to confirm water resistance after replacement?
A: Use a professional water resistance tester (air or water pressure). Pressurise to 3 bar (30m) and observe for bubbles around the case back. If no equipment is available, take the watch to a repair shop for testing.
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