The Nebula Award is an award given each year by the Science Fiction and Fantasy Writers of America (SFWA), for the best science fiction/fantasy fiction published in the United States during the two previous years (see rolling eligibility below). There is no cash prize associated with the award, the award itself being a transparent block with an embedded glitter spiral nebula. As opposed to the Hugo Award ballot, which is limited to works published during a specific calendar year, the Nebula Awards employ a rolling eligibility system. Each work is eligible to qualify for the ballot for one year following its date of publication. During this one-year window, SFWA members can "recommend" the work for the Nebula ballot.