MS2 and Fr Coliphage are two separate viruses with two different removal characteristics. That is why they are used as surrogates for other types of viruses. These viruses were selected, by both the EPA and the Military, because of their small size relative to other virus strains and the difficulty in removing both strains. They each are approximates 24-26 nanometers in size which makes them among the smallest of viruses. To see their relative size, we suggest that you visit The University of Utah Cell Size and Scale Chart. These viruses are comparable in size on that chart to the Rhonivirus. Therefore, MS2 and Fr Coliphage are the ideal viruses for use as indicators of a purification systems ability to remove viruses.
Special Notes: To understand the difference between the size of pathogenic bacteria and viruses, we suggest the following web link as it will give you a great visual of the difference: The University of Utah Cell Size and Scale Chart.
Slide the scale at the bottom to see the size of virus vs bacteria vs other potential contaminates and magnify to greater levels.
The fact that Black Berkey® purification elements have been tested to remove viruses to greater than the EPA purification standards suggests that contaminates larger in size, such as bacteria, should also be removed.
The MS-2 virus is 24-26 nm in size. The Fr Coliphage virus is 25nm in size. In other words, they are smaller than the hepatitis virus at 45mn and the rhinovirus at 30nm both referenced on the chart.
For more information on the MS-2 virus: MS-2 – Wikipedia
For more information on Bacteriophages in general: Bacteriophages: Update on application as models for viruses in water