Many divers watches use a compression or a press fitted crystal. These, in some cases, will have a crystal gasket to insure the maximum water resistance possible. Gaskets in watches are a vital part of their water resistance, so it’s important to consider them when servicing a watch. Whenever the crystal is replaced, the accompanying gasket should also be replaced. It usually gets damaged or it may stick to the crystal making it difficult to see how to put the new one in. Use this guide to learn how to measure for a new crystal gasket and crystal.

Start by measuring the inside diameter of the case opening where the crystal sits in. With a digital gauge, open the jaws and measure inside the case at the lip to get the diameter of the gasket needed.

Repeat this step to get an accurate measurement for the diameter.

Use the depth gauge on the digital gauge to measure the thickness of the gasket you need. Open the jaws of the digital gauge and place the end of the gauge inside the case just on the lip. Close the jaws until the end of the gauge rests on the top of the case opening. Repeat this measurement to verify it is correct. Use this measurement as the height or thickness of the gasket.

With the diameter and the thickness measurements, head over the to order a new crystal gasket.

The crystal gasket should be flush with the case or sit just below the top of the case. It should not stick out of the case,

Once you have your crystal gasket installed you can find what size crystal you need. With the digital gauge, measuring the opening of case from the inside of the crystal gasket. With this measurement you now know what size crystal you need to complete your repair. Use the measurement you have as the diameter of the crystal, and the height of the gasket for the thickness of the crystal.

For help on how to replace a watch crystal gasket, click here.