Level 1. Oysters are divided into one to four grades based on freshness, size, origin and meat quality, with Grade 1 being the highest grade. Rushan oysters are aquatic products certified by ASC and are also national geographical indication products, reaching the first level of raw eating level. Rushan oysters are bivalve shellfish of the order Oyster. They are mainly distributed in Rushan Pass and Langnuankou. They are also a specialty of Rushan City, Weihai City, Shandong Province.