Upgrade Items (Crafted Gear)
Upgrade Items for Crafted Gear are endgame tokens that are used to Augment crafted gear at vendors in the Endgame Hubs. Upgraded endgame crafted gear first began in Stormblood patch 4.3. The upgrade improves the gear's item level by 10, and it remains dyeable (as crafted gear typically is).
Unlike with tomestone gear, this is a two-part process. First you need to turn in the base-Augmented gear to a vendor in that expansion's Endgame Hub to receive a voucher. Then you need to purchase an additional item with Allagan Tomestones from the vendor. With both vouchers and the upgrade item, you can exchange for the Augmented gear. This voucher process means the gear you craft and the gear you exchange for do not have to be the same. For example, you can turn in Scouting gear and exchange the vouchers for Fending gear. Or you can turn in Foot gear and buy Hands instead.
In another departure from the tomestone gear process, Upgrade Items for Crafted Gear are not phased out when a new expansion releases. However, the additional item is transitioned to 
Poetics with the tomestone rotation.
