This Atomic Clock is always split second accurate and sets itself automatically from radio signal broadcast from the National Time Observatory in Colorado. The Shower Clock has a large suction cup with unique locking action to hold on any smooth surface like wall, tile or mirror for space saving. The Digital Clock digits are 3/4" high with display of month, date and day of the week, too. Round shaped cabinet is 3 1/2" in diameter. Metallic silver finish. Quality made throughout. Operates on 1 \"AA\" battery (sold separately)