The TR-55 oxygen transfiller is the most economical way to fill your cylinder by utilizing the gauge on the cylinder. One side has a CGA-540 nut & nipple with an O-ring seal, while the other end is equipped with a large hand nut with bare nipple. This allows you to slowly and safely bleed the line so the fittings can be easily removed from the cylinder. This transfiller is also available in a DIN-477-9 Swiss-Euro version. Standard length 18 inches (45.72 cm). Custom transfiller lengths are available on request.