The Magnetic Big Timer features a 60 minute countdown with alarm. Wind up clockwise one full turn to " 0" to set spring for alarm. Dial back counter clockwise to set red pointer at desired minutes. Alarm will sound once time has elapsed. Large, strong magnet on back lets you easily attach timer to magnetic whiteboards, steel filing cabinets, steel lockers, refrigerators, and more. Measures 7.5" diameter.