Constructed with two sharp needles and a self-contained light bulb, the test probe can be used at any point along a conductive tape run for electrical testing or finding a tape run under wallpaper. Simply push the needles into the copper strips and, if electricity is present, the enclosed bulb will light. The .175" pin spacing makes this handy tool usable with any tape system. It also provides proper spacing for placement of the eyelets when installing the sconce or chandelier adapters. Comes with snap top safety cap. Overall length approximately 2".