Dwyer Series Mark II 25 Molded Plastic Manometer, Inclined-Vertical Scale, 0 to 3 inH2O Measuring Range, Red Gauge Fluid, 0.826 sp. gr. (Limited Edition)

I am using this to monitor the pressure between two layers of plastic covering my greenhouse. It appears to be accurate and working well. Installation was easy. If it was less expensive, I would buy another one to monitor my a/c air filter. (If I were selling this item, I would price it around $29.95. JMHO)

My application is for monitoring the HVAC air handling to let me know when to change filters. And it works great for that.