A device for delivering respiratory gas directly into the nose of a user, for example for use in the treatment of sleeping disorders, in particular sleep apnea. This device for delivering respiratory gas directly into the nose of a user includes a hollow elastic membrane insertable into a nostril of the user and a part, inserted in the cavity of the elastic membrane, which part has a passage extending from one end to an opposite end of the inserted part, and it is characterized in that the inserted part further includes breathing channels which are located in the wall of the inserted part and extend from one end to an opposite end of the inserted part. The invention also relates to a method for producing the device according to the invention, a set and a system for delivering respiratory gas directly into the nose of a user, and a method for assembling the system according to the invention.