Poolmaster 52558 18" Clock/Thermometer/Hygrometer - Black 3-in-1 clock for indoor or outdoor use Clock, thermometer, and hygrometer for measuring humidity Weather-resistant with durable metal frame with baked enamel finish Clock features battery-operated quartz movement (batteries not included) Large easy-to-read roman numerals Battery-operated - requires 1 AA battery (battery not included) 18" diameter