Abstract: An electric transmission conductor support insulator made of plastic material for mounting on the top of a utility pole basically includes an elongated cylindrical body having a top end and a bottom end, a longitudinal bore within the body extending through the bottom end and tapering inwardly toward the top end, at least one circular ledge extending laterally from the body. The ledge has an upper surface, a lower surface and a side surface, the upper and lower surfaces are positioned normal to the longitudinal axis of the body, the lower surface being larger in diameter than the upper surface with the side surface sloping inwardly toward the body from the lower surface to the upper surface, and there is a circular notch in the side of the body juxtaposed above the ledge which notch is sized to admit a substantial portion of a conductor to be supported by the insulator.