Inside/Outside Couplings have one Small-End which fits inside Spiral Pipe or Metal Flexhose and one Large-End which fits outside Spiral Pipe or Metal flexhose. The 03IO will fit 80mm machine collars. When using I/O Coupling, install in direction of air flow for a smoother inside surface. 20 gauge galvanized construction.

Small-End is O.D. even inch – 1/16″.  Large-End is I.D. even inch + 3/16″.