Of the many uncertainties that a boater faces often the largest is the accuracy of his fuel gauge The fuel sending unit's in a majority of production boats today use a simple float style design that in some instances, provides limited accuracy due to fuel slosh and the up and down bouncing of marine power boating If you have or are experiencing the symptoms we've got the answer for you, this double tube design measures the amount of air trapped between the tubes to accurately and precisely measure your current fuel load This design makes installation and calibration for use with 33-240 ohm gauges