This tool is used to see what the sugar content is in the sap. The range we look for is between 1-3 Brix. 3 being the best, 1 being the worst. With out current set up, we test the sap right out of the tank before it goes into the evaporator. We take a drop and place it on the lens. We then hold it up to the light and look inside. Reading the blue coloring on the gauge, we are right at the 2 mark.