For use on most spark ignition gasoline powered engines - Inductive pickup - Wrap one wire around the spark plug wire, connect the other to bare metal ground, fasten the meter in any convenient location. Can be fastened with screws, or use the sticky foam 2-sided tape and stick it in place - Displays hours and tenths. LCD display. Unit is permanently sealed, but we are aware that some people have had success with disassembling the unit and replacing the battery, extending the unit's service life. Battery is typically good for between 1 to 3 years.