Abstract: A tool for controlled, uniform insertion of insulated conductors into insulation piercing contacts in an electrical connector unit includes a holding lug to engage the conductor and apply a holding pressure adjacent the free end of the conductor in one end of a terminal element channel of a contact member, an insertion blade for pressing the conductor into an insulation piercing notch of the terminal element, and an insertion guide to engage the conductor at a point immediately beyond the strain relief retainer of the connector unit and guide the conductor into the strain relief retainer. In one embodiment the tool is part of an adapter which becomes anchored to and remains as a part of the connector unit.