Read from the World of Warcraft client build files.
How Firebird's Headpiece Compares
Who It Suits
Mail is the armor type Evoker, Hunter and Shaman wear. With Agility or Intellect, Firebird's Headpiece suits Beast Mastery, Marksmanship and Survival Hunter; Elemental, Enhancement and Restoration Shaman; Devastation, Preservation and Augmentation Evoker.
Transmog Sets
Firebird's Headpiece is part of the transmog set Regalia of the Firebird (Shaman only). The other 16 pieces:
Built from the World of Warcraft client build files and recorded Auction House snapshots.
Where Firebird's Headpiece Fits
Other Items Named Firebird's Headpiece
2 other items in the current build are also called Firebird's Headpiece. Same-name entries are usually a different rank, faction, quest stage or reward track of the same object.
Blizzard numbers items as they are created, so the named items next to ID 87141 (87136 to 87146) were usually added in the same batch as Firebird's Headpiece: the same quest line, zone, vendor or reward set.