Dwyer Instruments air velocity kits comprise a manometer designed for measuring positive, negative & differential pressures of natural gases & air in boilers and HVAC equipment. They can also be used to monitor the air velocity when used with a Dwyer pitot tube and AV calculator. These 475 Series differential manometers feature dual push pads on the front panel to control the ON/OFF, Auto-Zero and pressure unit selection functions. They are further integrated with a rugged yet lightweight aluminium case for protection against accidental drops & blows and a large, easy-to-read LCD screen for enhanced monitoring in poor or bright light conditions. Choose from a wide range of these air velocity kits, available in 5 & 10 psi pressure rating options on Raptor Supplies.