Customizable mask and method of sizing

A mask for use in providing a flow of a treatment gas to the airway of a user, the mask comprising:

• a frame having:
• a front face positioned to face away from the user when the mask is disposed on the face of the user;
• a concave shaped rear face positioned to face toward the user when the mask is disposed on the face of the user, the rear face defining a cavity, the cavity being structured to receive the flow of the treatment gas therein and to receive at least one of a portion of a nose of the user and a mouth of the user therein;
• an opening defined in a central portion of the frame, the opening passing between the front face and the rear face, the opening being structured to have a conduit coupled thereto for receiving the flow of the treatment gas;
• and
• a number of deformable zones defined in the frame, each deformable zone being structured to receive a removable insert, each deformable zone being structured to adapt to at least one of a size or a shape of the removable insert received therein;
• and
• a conformable cushion coupled to the frame and structured to sealingly engage about at least one of at least a portion of the nose or the mouth of the user.