Vacuum gauges measure vacuum (negative pressure) by inches of mercury. We offer vacuum gauges which measure from -30 inHG to 0, 15, 30, 60, or 160 PSI. We also offer compound (or “boost”) gauges. Both our vacuum and compound gauges come in dial sizes from 1 ½” to 4” with center back or lower mounts (aka “bottom mounts"). They are available in both glycerin oil filled or dry utility versions. HOW TO ORDER: To order a vacuum gauge, simply click on the icon (see products below) with the style (liquid filled or dry) with the mount type you need. Then, choose the dial size and pressure range from the list provided. Vacuum gauges will have a part number, a dash, then a “V”. For example, “PB204L-V00” is a 2” vacuum, glycerin filled, lower mount, ¼” NPT connection, measuring from -30 inHG to 0 PSI. The number after the V represents the positive range of a compound gauge. For instance, products ending with V15 represents a pressure range of -30 inHG to 15 PSI.