The Mastercool 98066 Analog Vacuum Gauge is designed to provide accurate readings every time. This bourdon tube type analog vacuum gauge is used for determining system vacuum. The large, 80 mm gauge makes it easier and more accurate to read than smaller gauges. The indicator needle, used for marking pressure for testing, provides a backup in case users forget to write the pressure down. Users can see if the pressure has changed with a quick glance. The barometric pressure compensation allows for the most accurate reading regardless of altitude or local weather conditions. This model includes a 1/4 in. flare female swivel nut connection which allows for direct attachment to the system or vacuum pump.