Jewels are synthetically produced rubies, which are used to reduce friction in the main bearings of the moving parts of a watch movement.

Quartz watches with few moving parts have only a few jewels, mechanical watches have 17 to about 50 jewels depending on the complexity of the movement.

Jewels are used as hole stones or capstones, and in addition also at lever pallets and at the ellipse.

A lot of jewels in a movement does not necessarily signify a higher quality. On the contrary, often cheap wristwatches with a high number of jewels noted on the dial intend to suggest a high quality. However, many of these are not really needed or are not at the necessary places. A precision movement with manual winding needs at least 15 functional jewels 10 jewels, 2 capstones for the balance wheel, 2 pallet stones for the lever and one impulse stone (ellipse). An optimum configuration is given with 18 jewels.

For complicated watches such as with automatic winding, chronograph or repetition, the number of jewels necessarily increases.