Jewel bearings are used in precision instruments where low friction, long life, and dimensional accuracy are important.
[2] The advantages of jewel bearings include high accuracy, very small size and weight, low and predictable friction, good temperature stability, and the ability to operate without lubrication and in corrosive environments.
[3] Disadvantages include brittleness and fragility, limited availability and applicability in medium and large bearing sizes and capacities, and friction variations if the load is not axial.
Manufacturers traditionally listed the number of jewels prominently on the watch face or back, as an advertising point.
In such instruments, jewel bearings are often used as pivots for their needles which need to move reliably and with low variability even when measuring small changes.