Gaskets

A well-fitted watch case gasket is what stands between your movement and the outside world. These small rubber or silicone rings ensure your watch stays waterproof, whether you’re washing your hands or diving deep. Replacing gaskets is an essential step during every case service — even a tiny crack can cause condensation inside your sapphire crystal. Builders using Seiko NH35 or ETA 2824 cases often keep spare sets to avoid downtime during assembly. You can easily match gasket thickness using a caliper and restore perfect sealing with a touch of watch oil lubricant.

To learn how to properly reseal a diver case, check our guide How to Keep Your Watch Waterproof. After replacing the gasket, test your assembly with a case opener and secure the backplate. For a full waterproof rebuild, use sapphire crystals and screw-down crowns. Pair this maintenance with tools from our Watch Repair Kit for a complete professional setup. Gaskets might seem minor, but they’re the unsung heroes of durability in every watch case replacement.