3 Percentage Accuracy for Stationary and Portable Applications. Series Mark II Molded Manometers are of the Inclined Types. The Curved Inclined Tube of the Model 25 Gage Provides Higher Ranges with More Easily Read Increments at Low Readings. The Model 25 is Excellent for General Purpose Work. The Model 40 Inclined Gage Provides Linear Calibration and Excellent Resolution Throughout its Range. The Model 40 is Ideally Suited for Air Velocity and Air Filter Gage Applications. Both Gage Types are Capable of Pressure Measurements Above and Below Atmospheric as Well as Differential Pressure Measurements. Included with Each Mark II Manometer are Two Tubing Connectors for 1/8 Inch Pipe or Sheet Metal Ducts, Two Mounting Screws, 1 Ounce Bottle of Indicating Fluid, Red and Green Pointer Flags and Complete Instructions.