Highest quality, versatile open-gap spark checker, for 1 to 8 cylinders. This "sparky" can be seperated into two 4-wire halves by loosening two wing nuts. Furnished with two ground wires for seperate 4-wire use. Sliding mechanism adjusts four gaps which are marked from 1/4 to 1/2 inchas well as in millimeters. Black background for easy visibility is recessed to prevent carbon tracking. Molded Valox is highly resistant to chemical, UV and Physical damage.