Flat watch gasket sheet 0.30 mm

This 0.30 mm red case-back gasket is a watchmaking-grade O-ring designed to restore the water resistance of screw-down or press-fit case backs on Rolex, Omega, Seiko, Tissot, Longines and many other Swiss and Japanese movements. Calibrated thickness 0.30 mm, Shore A 75, suitable up to 10 ATM.

About this part

This red gasket is a classic Swiss-style case-back gasket. The red colour comes from a specific NBR compound that improves UV visibility on the workbench and indicates a slightly harder Shore A 75 grade dedicated to screw-down case backs. Like every quality gasket, it acts as the primary barrier between the inside of the watch and the outside world. Without an intact case-back gasket, perspiration, dust and ambient humidity reach the movement plates, the balance and the dial; lubricants such as Moebius 8217 lose their viscosity, corrosion attacks the steel parts and the running rate of the watch drifts within weeks. Replacing this 0.30 mm gasket during every battery change or every service is the single most cost-effective maintenance operation on a modern watch.

Technical specifications

• Calibrated cross-section thickness: 0.30 mm
• Material: NBR, hardness Shore A 75
• Alternative grades available: FKM / Viton (chemicals, ozone), EPDM (steam), Hytrel (mechanical fatigue)
• Working temperature: -20 degC to +70 degC
• Pressure rating once correctly torqued: up to 10 ATM
• Lubricant: Moebius 8217 silicone grease, watchmaking standard
• Compatible with: Rolex Oyster style case backs, Omega Seamaster, Seiko diver, Tissot, Longines, generic Swiss and Asian movements
• Origin: European watchmaking-grade compound, cold moulded and individually controlled

When to use this part

This 0.30 mm reference is among the most common in mid-range and luxury watches. Use it during a full service, a battery replacement on a quartz watch, after a pressure test failure on the case-back side, or whenever you see visible deformation, flattening, cracking or hardening of the original gasket. A 0.30 mm gasket that has lost its round profile no longer recovers under torque and must be replaced.

How to install it step by step

1. Measure the groove diameter on the case-back side with a digital caliper.
2. Remove the old gasket with a wooden or plastic pick, never with steel tools that would scar the groove.
3. Clean the groove with isopropyl alcohol; dry with a lint-free wipe.
4. Lay the 0.30 mm gasket flat in the groove without twisting.
5. Apply a thin film of Moebius 8217 silicone grease around the gasket.
6. Refit the case back with the correct torque and run a 3 ATM dry test, then a wet pressure test.

Quality, origin and packaging

This gasket is moulded in Europe from watchmaking-grade NBR rubber, then individually checked for ovality, surface finish and dimensional accuracy. Packaging is dust-tight to preserve the elastic memory and the colour stability over years of shelf storage.

Frequently asked questions

Will this fit my Rolex Submariner or Omega Seamaster? The 0.30 mm is the cross-section thickness; you must match the inner diameter of your case-back groove to your reference. We cover all standard diameters in this section.

How often should I replace this gasket? Every battery change on a quartz, every full service on a mechanical, and immediately if a pressure test fails.

Can I lubricate it with anything other than Moebius 8217? Any neutral silicone grease will work; avoid mineral oils that would swell the NBR.