Bezel
A bezel is the part of a watch that surrounds the crystal.
Most bezels are differentiated visually from the body of the case. Watches without a distinct ring around the crystal can be called "bezel-less" or "integrated". The bezel can be an important cosmetic element as well, as is the case with the famous "hobnail" bezel on the Patek Philippe Calatrava and extravagant ring on the Blancpain Fifty Fathoms.
In dive watches the bezel is provided with minute markers, and is designed to be rotated to measure dive time. Blancpain invented a uni-directional bezel which turns counterclockwise so dive time can not easily be increased accidentally. Bi-directional rotating bezels are also useful in field watches for solar navigation. Other sports watches are equipped with a bezel with a tachymeter, telemeter, or slide rule.