Synthium-Studded Belt is a rare-quality style item that unlocks the Greco-Roman waist costume style when used.
Source[]
The Synthium-Studded Belt can be obtained as an item drop within The Vault, an instanced minigame zone that players can enter daily. The Vault is accessed from a player's On Duty menu.
Item drop[]
Style unlock[]
Upon using the Synthium-Studded Belt, a character unlocks the Greco-Roman waist costume style, which can be accessed at any time from the Style Window.