The balance spring or the hairspring of a watch is a highly delicate, flexible coil attached to the balance wheel, controlling its swing. The balance spring's sensitivity ensures that the balance wheel's swing returns it to the normal position of rest after every oscillation and keeps the motion constant and regulated. This spring's precision is imperative in ensuring the watch attains timekeeping accuracy since minute variations might jeopardize its operation. Balance springs are also occasionally manufactured using advanced materials, such as silicon.
This makes them resistant to temperature variations and external magnetic influences, significantly increasing the component's lifespan. This tiny element is of great importance for the behavior of a mechanical watch; without it, it would wear out extremely fast and be unable to keep time well over any length.
