AXI Fine and Water Block Filters are the most efficient, reliable, and cost effective filtration products on the market. For a diesel engine fuel filter to remove contamination from the fuel system, it must be very efficient, ideally below 4μ. The efficiency of a filter is reported as a Beta Ratio and is the recognized industry standard for reporting filter efficiency. The Beta Ratio is defined as the difference between the number of particles larger than a given size upstream of a filter to the number of particles of the same size downstream of the filter. More can be learned about filter standards and efficiency at our Diesel Engine Fuel Filters page.