Halo numbers are a system which orders official Nine Inch Nails releases. They correspond to the sequence in which the releases were made, and are named by the word “Halo” which precedes the number on the release. For example, the fifth NIN release, Broken, is adorned with the phrase “Halo Five”. Halo numbers are sometimes modified for alternate versions of a release. Promotional-only releases do not have their own halo numbers, although the promotional singles for “Piggy” and “Hurt” were labeled as “Halo Ten”, a title later officially used for Further Down the Spiral. A U.S. promo for “Into The Void” is mislabeled as Halo 16. This number actually belongs to Things Falling Apart.