Kif is a common shock protection system used in mechanical watches. It is manufactured by the Parechoc company, and these terms are often used to describe the shock protection system itself.
Kif was developed in the 1930's. It prevents a watch balance staff from breaking by allowing it to move slightly, both laterally and vertically, using a spring-mounted jewel setting. Kif can be recognized by the golden 3-leaf or 4-leaf clover shaped spring clip around a ruby at the top of the balance.
Kif is also the name of the company that produces these shock absorption systems. It is related to Rolex, which favors Kif shock protection to this day.
Kif makes both removable and hinged anti-shock mechanisms