Our MicroTight Union Assembly is used specifically to connect capillary tubing together. It features a 0.015″ thru-hole which adds only a small amount of additional flow-path volume to help ensure proper chromatographic results. It has a 360umOD and includes (2) F-152 fittings and (2) P-416BLK Micro-Fingertight Fittings. Brochure