The Salter Labs Oxygen Concentrator Adapter Tubing is a short connecting oxygen tubing that bridges connections to humidifier bottles through the form of an adapter. The connecting tube is quite universal and can fit almost any humidifier bottle with a screw-type connection. The clear oxygen tube is made with a ribbed connector to offer a secure and snug fit without damaging connecting points to the adjoining tube. The clear color of the tube allows you to see the oxygen tube rated for oxygen concentrator use if any blockage or breakage was to occur within the tube itself. 21″ long.