Most anglers agree fish bite better two hours before and two hours after a high tide. This clock’s cycle is set for semidiurnal tides: two high tides and two low tides per day. It displays time to high and low tides, as well as to the ebbing and flooding half tides. A gradation around the scale indicates best fishing times. It also has a brass lacquered case. The tide clock's cycle is geared to Atlantic Coast tides. Requires 1 AA battery (not included). Size: 6" (diameter) x 2-3/4"(depth).