The fen took the form of a copper coin with a hole through the center, similar to the yuan. Five fen were worth 1 yuan, 100 fen were worth 1 ch'ao or 1 tael, and 1000 fen were worth 1 ch'ien. If transported to Faerûn circa 1357 DR, 1 fen would be treated as worth 1 copper piece.
Thanks to their holes, collections of fens and yuans were threaded on strings in amounts of 50–100, which was convenient for counting and carrying them. These cash strings could be worn on the wrist and tucked inside the sleeve.