The nozzle performance charts found on this website have two columns that show the approximate precipitation rates for the sprinklers at a given pressure, radius (spacing) and flow. The column on the left with the Square Precipatation Rate Symbol symbol shows the precipitation rate for the sprinklers when they are laid out in a square pattern. The formula used to calculate the precipitation rate in this case is the “Sprinkler Spacing Method – Any Arc and Any Spacing” equation, see the Hunter Catalog for more information. The column on the right with the Triangular Precipatation Rate Symbol symbol shows the precipitation rate for the sprinklers when they are laid out in an equilateral triangular spacing pattern. The formula used to calculate the precipitation rate in this case is the “Sprinkler Spacing Method – Equilateral Triangular Spacing” equation, see the Hunter Catalog for more information.