Mask ports (180) for attaching supplemental oxygen tubes (510) or measurement devices to a respiratory mask are downwardly directed and recessed into the base (110) of the mask frame (100). The ports may comprise a pair of downwardly extending tubular spigots (185) each housed in a respective recess (190) in the base (110), with a shallow bridging recess (290) there-between for receiving a bridging piece (300) of a closure cap (280).
