Watch Bezels Explained: Fixed, Rotating, Tachymeter and More

The bezel is the ring around the crystal, and on many watches it does real work. Some are purely decorative, while others are measuring tools for divers, pilots and drivers.

A fixed bezel simply frames the dial. Dress watches often have thin polished bezels, and a few use a coin-edge or fluted pattern that adds a classic detail. Fluted bezels are also traditionally associated with some famous steel-and-gold sports watches.

A rotating diver's bezel is the most recognisable tool bezel. It is marked in minutes for the first twenty or so, and it turns in one direction only. You line the zero marker up with the minute hand at the start of a dive, then read the elapsed time. The one-way action means that if it is knocked, it errs on the side of showing less time remaining.

A GMT bezel, often with 24 hours marked, works with a fourth hand to track a second time zone. Some can be turned in both directions to track a third zone, which is useful for frequent travellers.

A tachymeter scale, usually engraved on a chronograph bezel, lets you work out speed from elapsed time over a known distance. Start the chronograph at the first marker, stop it at the second and read the speed from the scale. It works for any measured distance, as long as the time is under a minute.

Bezel inserts come in aluminium, steel, ceramic and sapphire. Ceramic resists fading and scratches better than aluminium, while aluminium gives a warm vintage patina over time. Check the grip and the click action when trying one on.