The Morrison Fig. 818 Clock Gauge is used for measuring liquid level in aboveground storage tanks. Readout format is on a standard 12 hour clock face. Small hand represents feet and the large hand inches. Gauge can be read up to 20-30 ft. away to within 1/8". Maximum measurement capability is 12 feet. The gauge can be rotated 3600 after mounting. The standard float will pass through a 2" opening.