8.5" Tide Clock Special for fishermen, surfers, mariners, seaside property owners, anyone who enjoys to track the coastline tides, ensure you always grasp the information where the tide condition it is and when the tide rising and ebb. The tide clocks work well on the east coast, slightly the Gulf of Florida. It works on the West coast, Gulf of Mexico - it needs to be calibrated regularly. Features colorful designed graphics for high and low tide, with quality ABS plastic water resistant case with rear cover. The locking rear cover with 3-point secure screw mount system allows mount it on the wall, it holds the clock in place on your sea bound vessel. TECHNICAL SPECIFICATIONS: Clock is approximately 8.5" in diameter and 1.6" deep, intended for indoor use. The clock requires one AA battery (not included). For optimal performance and longer lifespan, the use of a Carbon Zinc battery is recommended. 8.5" Tide Clock Special for fishermen, surfers, mariners, seaside property owners, anyone who enjoys to track the coastline tides, ensure you always grasp the information where the tide condition it is and when the tide rising and ebb. The tide clocks work well on the east coast, slightly the Gulf of Florida. It works on the West coast, Gulf of Mexico - it needs to be calibrated regularly. Features colorful designed graphics for high and low tide, with quality ABS plastic water resistant case with rear cover. The locking rear cover with 3-point secure screw mount system allows mount it on the wall, it holds the clock in place on your sea bound vessel. Clock is approx. 8.5" diameter and 1.6" D Intended for indoor use. Clock requires one AA battery (NOT included).