Insulates electrical wire/cable which is attached in the groove. Screwed into the cross arm of a power pole. Non conductive so electricity doesn't short out to the ground.Used on power poles in the Kiewa ValleyClear blue tinted glass insulator - bell shaped at the closed end. Deep, wide groove towards the wide open end. The wide end is inscribed and opens to a decorated edge of small balls around the circumference. Inside there is a cylinder which is threaded for screwing onto a power pole. This cylinder is shorter than the outside part."Hemingray - 19" "Made in U.S.A."electricity. power lines. insulator. hemingray.