We sell hourmeters (or counters) made by ENM, Murphy, VDO, Datcon and Stewart Warner. Hourmeters are used to log the number of hours an engine has been running, which is useful for maintenance. Most hourmeters are electric and require no sensor or sending unit. We also sell hourmeters by ENM that are activated by vibration. They are powered by an internal lithium battery and do not require wiring. Our round hourmeters 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"). Square hourmeters (often called mini-meters) fit a hole 2 inches across.