A patient interface system to treat a respiratory disorder of a patient, the patient interface system comprising: a positioning and stabilising structure including: a back portion ; a pair of upper straps extending from the back portion; and a pair of lower straps extending from the back portion; and a patient interface including: a plenum chamber comprising at least one plenum chamber retention feature ; a seal forming structure ; a patient interface frame comprising: a pair of lower attachment points for releasable attachment to a respective lower strap of the pair of lower straps; and at least one patient interface frame retention feature each configured to releasably attach the patient interface frame to the plenum chamber by a releasable connection with a corresponding one of the at least one plenum chamber retention feature wherein the patient interface frame is releasably connected to the plenum chamber about a periphery of the plenum chamber; and a pair of rigidiser arms each connected to the patient interface frame at a connection point, the pair of rigidiser arms further including a pair of upper attachment points, wherein the pair of upper straps are adapted to be releasably attached to the pair of upper attachment points such that, when donned by the patient, sealing force vectors generated by the pair of upper straps are vertically offset relative to the connection points and parallel to the patient's Frankfort horizontal plane, and wherein the patient interface does not include a forehead support. a positioning and stabilising structure including: a back portion ; a pair of upper straps extending from the back portion; and a pair of lower straps extending from the back portion; and a back portion ; a pair of upper straps extending from the back portion; and a pair of lower straps extending from the back portion; and a patient interface including: a plenum chamber comprising at least one plenum chamber retention feature ; a seal forming structure ; a patient interface frame comprising: a pair of lower attachment points for releasable attachment to a respective lower strap of the pair of lower straps; and at least one patient interface frame retention feature each configured to releasably attach the patient interface frame to the plenum chamber by a releasable connection with a corresponding one of the at least one plenum chamber retention feature wherein the patient interface frame is releasably connected to the plenum chamber about a periphery of the plenum chamber; and a pair of rigidiser arms each connected to the patient interface frame at a connection point, the pair of rigidiser arms further including a pair of upper attachment points, a plenum chamber comprising at least one plenum chamber retention feature ; a seal forming structure ; a patient interface frame comprising: a pair of lower attachment points for releasable attachment to a respective lower strap of the pair of lower straps; and at least one patient interface frame retention feature each configured to releasably attach the patient interface frame to the plenum chamber by a releasable connection with a corresponding one of the at least one plenum chamber retention feature wherein the patient interface frame is releasably connected to the plenum chamber about a periphery of the plenum chamber; and a pair of rigidiser arms each connected to the patient interface frame at a connection point, the pair of rigidiser arms further including a pair of upper attachment points, wherein the pair of upper straps are adapted to be releasably attached to the pair of upper attachment points such that, when donned by the patient, sealing force vectors generated by the pair of upper straps are vertically offset relative to the connection points and parallel to the patient's Frankfort horizontal plane, and wherein the patient interface does not include a forehead support. <EOS>