This Morrison 818 Clock Gauge is used for measuring the liquid level in aboveground storage tanks. The readout format is on a standard 12 hour clock face. The small hand represents feet and the large hand represents inches. This gauge can be read from 20-30 feet away to within 1/8″. Maximum measurement capability is 12 feet. The gauge can be rotated 360 degrees after mounting. The standard float will pass through a 2″ opening.