The Dwyer Instruments 477 is a highly accurate digital manometer designed for precise measurements in the field of HVAC, plumbing, and pneumatic systems. With a range of up to 20 inH2O and user-selectable engineering units, this portable instrument provides accurate and reliable readings for a wide range of applications. Built with a durable and ergonomic design, the Dwyer Instruments 477 0-20" W.C. reads positive, negative, and differential pressure. It is the ideal choice for professionals in need of a reliable and easy-to-use digital manometer.