In order for an etrog, used as one of the four species for Sukkot, to be kosher it must have an intact stem, therefore they are usually placed in protective cases. These boxes can be made of any material, there are no rules as to their shape or material. Hiddur mitzvah, the beautification of the mitzvah especially applies to the etrog; to use the largest etrog and the most artistic objects in order to fulfill and beautify the mitzvot.