ARYA Airtivo Portable Oxygen Concentrator Backpack checklist 7 DAY FREE TRIAL Rustproof frame: Engineered with heavy duty 25 Internal Base Width Rustproof frame: Engineered with heavy duty aluminum that will never rust This is a must have accessory for those needing to charge up more than one power cartridge (battery) at a time The padded and adjustable shoulder straps for both shoulders make carrying your ARYA Airtivo comfortable and it is still easy to access the controls on your device without removing it from the backpack The ARYA Airtivo Backpack not only makes carrying your ARYA Airtivo portable oxygen concentrator easy