1. Flange: A protruding outer edge at the outer end of the mouth can prevent swallowing and excessive penetration.
2. Dental pad: The width of the occlusal area between the dental pad and the teeth should be enough to contact two or three teeth, so that the occlusal pressure can be evenly distributed to the teeth in contact.
3. Pharyngeal curvature: the curvature of the inner end of the pharyngeal curvature is adapted to the anatomy of the mouth, tongue and back of the pharynx.