Much easier to understand than tide tables, this tide timer is especially beneficial for the individual needing information on tidal activity (boaters, beachcombers and fishermen). It operates on moon time which has a 24 hour 50 1/2 minute day. The hand shows how many hours until the next high or low tide. On the Atlantic coast, it never needs adjustment (although the actual time of the tides is affected by other factors, it varies only slightly from the rhythmic cycle). On the Pacific coast, it may be calibrated to different coastal locations to compensate for the more significant variations which occur in the ocean. Not for use on the Gulf of Mexico. Round brass housing. Wall mount only. Runs on one AA battery. 4 1/2" Diam. x 1 1/2" D. (1 lb.)