Luer-tip and Lock needles can be connected to PTFE tubing with an outer diameter of 3 mm or 1/8 inch. Luer Lock Male Connector The Luer-lock needles can be connected to PTFE tubing with an outer diameter of 3 mm or 1/8 inch. Luer Lock Female Connector The Luer-lock syringes can be connected to PTFE tubing with an outer diameter of 3 mm or 1/8 inch.