The balance wheel is a crucial component in mechanical watches, serving as the timekeeping element that regulates the movement of the watch. It is a wheel that oscillates back and forth, driven by the energy stored in the mainspring and released through the escapement. The balance wheel works in conjunction with the hairspring, a delicate spiral spring, to control the rate at which the wheel oscillates. This oscillation is what ultimately determines the accuracy of the watch, as it divides time into equal segments.

The balance wheel's design and material are critical for ensuring precision and stability. Typically made from metals like Glucydur or beryllium copper, the wheel must be resistant to temperature changes and magnetic fields to maintain consistent performance. The balance wheel's frequency, measured in beats per hour, is a key factor in a watch's accuracy. Higher frequencies generally lead to better precision, as they allow for finer time division.

In horology, the balance wheel is often compared to the pendulum in a clock, as both serve the purpose of regulating time. Its invention and refinement have been pivotal in the development of accurate timepieces, making it a symbol of precision engineering in watchmaking.