①The crown has a rounded, fan-shaped outline.

②From the proximal view, the crown axis tilts toward the lingual side.

③The occlusal outline is either round or square.

④The grooves on the occlusal surface vary from H-shaped to Y-shaped to U-shaped, depending on the development of the cusps.

⑤The lingual cusp is large, and a secondary cusp may also appear.