The MK.III adaptor enabled the use of E-series, G-type and H-type masks in older aircraft fitted with early oxygen systems. These adaptors were also used to connect masks to portable (walkaround) oxygen bottles. They were fitted with a MK.IIIB* adaptor at one end and a MK.IVA socket at the other. Here we have the tube section alone. It is in very good flexible condition with no evident cracking or deterioration. Stock code O21068.