Watch jewels are tiny pieces of synthetic ruby or sapphire set into holes within a watch movement. 

 

These gems primarily help to reduce friction and provide a hard, smooth surface to allow metal compounds such as the wheel trains to rotate freely. 

 

The friction of these jewels aids accuracy, and their durability helps to increase the life of bearings. 

 

Modern watches have no difference in performance between ruby and sapphire jewels. 

 

Jewels are typically placed at particular areas of stress or strain within the watch movement.