Primal Gladiator's Wyrmhide Robes is part of the transmog set Primal Gladiator's Dragonhide Armor (Druid only), which the Appearances collection lists in 2 versions. The other 16 pieces:
Items Numbered Next to Primal Gladiator's Wyrmhide Robes
Blizzard numbers items as they are created, so the named items next to ID 115860 (115855 to 115865) were usually added in the same batch as Primal Gladiator's Wyrmhide Robes: the same quest line, zone, vendor or reward set.