We sell PIC, Stewart Warner, and ISSPRO and VDO vacuum gauges. Vacuum gauges are essentially just pressure gauges, but instead of sensing air, fuel, water or oil pressure, they sense vacuum (the absence of pressure). These vacuum gauges are 2" inch in diameter, which is the standard hole size for aftermarket fuel, volt, pressure, amp and temperature gauges (speedometers and tachometers are typically 3 3/8"). Match the electrical vacuum gauge to its matching sensor - a VDO vacuum gauge should use a VDO vacuum sender. Mechanical vacuum gauges require a standard Pressure Tube Kit to provide the signal source. The tube may be cut to length as needed (unlike mechanical temperature gauge cables). All pressure tube kits work with virtually all vacuum gauges.