A device for treating sleep apnoea or snoring is described. The device occludes or pushes the mandible or lower jaw forward to maintain an open air passage. The device resembles a mouth guard with maxillary (upper, 02) and mandibular (lower, 12) splints whose respective protrusions (05l, 05r) and fins (22l, 22r) engage to push the mandibular splint (12) forward. The fins can be swapped or replaced with different designs and are attached to the mandibular splint by a pin (e.g. 15l).
