... 2. certificate,CE ,ISO13485 3. anti-crush tube,non-toxic PVC,medical grade,flexible. nasal oxygen tube helping breathing oxygen1.Made ... of non-toxic PVC,medical grade ,tubing color is green or transparent2.Tubing out ... ,oxygen uptake can be never stopped .9.pure color and soft texture gives users' more comfort Pure PVC Nasal Cannula with oxygen tubing