Ring snap ring (also known as ring snap ring): It is mostly used for isolated last molars and is inclined to the mesio-buccal (upper jaw) or mesiolingual (lower jaw) side. The snap ring surrounds almost the entire axial surface of the crown, and the snap ring arm has an elastic tip that ends at the mesio-buccal side of maxillary molars or the mesiolingual undercut area of u200bu200bmandibular molars. The cast ring-shaped snap ring can be designed with two (occlusal) rests at the mesial and distal (occlusal) margins. The non-retaining side snap ring arms should not be undercut, and should be supported by auxiliary clamp arms. The bent ring-shaped clasp only has mesial (occlusal) support, and the non-retaining side clasp arm should extend the base to the distal side to wrap around the base to reinforce and counteract the arm, so as to avoid the deformation of the clasp arm too long .