Abstract: A fitting assembly (10) mates an end of polymer micro-tubing (12) in fluid communication with an internally threaded connector (22) having an internal bottom wall (38). The fitting assembly includes a male nut (16) having external threads and a passage for receiving the end of the polymer micro-tubing. The fitting assembly additionally includes an insert (24) having an elongated stem (30) and an annular head (26). The stem projects from the rear side of the annular head for insertion into the end of the polymer micro-tubing. The annular head includes a forwardly projecting nose section (31). An elastomeric seal (40) is received on the nose section (31) and retained in place by a lip (33) included on the nose section. The seal is compressed between the head of the insert and the bottom wall of the connector.