Adjustable headgear tubing for a patient interface

A patient interface for sealed delivery of a flow of air at a therapeutic pressure of at least 4 cmH2O with respect to ambient air pressure throughout the patient's respiratory cycle in use, the patient interface comprising: a cushion assembly comprising: a plenum chamber pressurisable to the therapeutic pressure, said plenum chamber including a pair of plenum chamber inlet ports, each of the plenum chamber inlet ports being sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; a nasal seal-forming structure that is configured to seal around the patient's nose in use, the nasal seal-forming structure having a nasal hole configured to deliver the flow of air at said therapeutic pressure to the patient's nares in use; and an oral seal-forming structure that is configured to seal around the patient's mouth in use, the oral seal-forming structure having an oral hole configured to deliver the flow of air at said therapeutic pressure to the patient's mouth in use; a positioning and stabilising structure configured to hold the seal-forming structure in a therapeutically effective position on a head of a patient, the positioning and stabilising structure comprising: two gas delivery tubes, each of the two gas delivery tubes being connected at a first end to a corresponding one of plenum chamber inlet ports to deliver the flow of air to the entrance to the patient's airways via the cushion assembly, each of the two gas delivery tubes being configured to be positioned on a corresponding lateral side of the patient's head in use, each of the two gas delivery tubes being constructed and arranged to contact, in use, at least a region of the patient's head superior to an otobasion superior of the patient's head, and each of the two gas delivery tubes comprising a tab projecting in a generally posterior direction relative to the patient's head in use, the tab having a hole; a connection port configured to fluidly connect, in use, the gas delivery tubes with an air circuit to deliver the flow of air to the patient's airways, the connection port configured to be located, in use, superior to the patient's head; and a headgear strap assembly comprising: a length-adjustable rear strap, an end of the length-adjustable rear strap being configured to pass through the hole of the tab to removably connect the length-adjustable rear strap to the gas delivery tube and the length-adjustable rear strap being configured, in use, to pass a