Bien Mai is a type of sea pen shell that is triangular in shape, about the size of an adult hand, and resembles a half-closed fan. This species usually burrows deep into the seabed, wrapped in a dark brown shell that swells like a banana flower blossom.
Despite its impressive size, the body meat of the Bien Mai pen shell is quite soft and flavorless. All the essence of this seafood is concentrated in the two round, snow-white muscle buttons connecting the two shells, which locals call "coi" (adductor muscle). To harvest this valuable muscle, fishermen dive deep into the sea, crack open the shell, delicately separate the slimy body part, and clean it thoroughly.


