Currently, the comic book annual is still something of a rarity, its purpose in presenting "extra" material often served by "Special Edition"s that are released at random intervals (usually to fill a gap in a publisher's production schedule) rather than the set yearly schedule of an annual. In addition, Marvel Comics in particular has adopted a publishing schedule in which 13 or 14 issues of an ongoing series will be published within a year, rather than one issue for every month of the year; the material provided in the additional issues per year, in effect, replaces the material that would otherwise see print in an annual.