In Aion 2, old equipment cannot be sold directly. When your inventory is full of unused gear, players can process them through "Item Extraction" to exchange for upgrade materials and corresponding gear appearances.
To perform this action, first open the inventory named "The Cube" and click on the gear you wish to extract. Locate the beaker-shaped icon in the bottom right corner of the gear description panel; hovering over it will confirm it is the extraction command. Clicking it will take you to the extraction menu.
The menu displays the gear that will be lost and the items expected to be obtained. The extraction is only completed after player confirmation. Each operation also costs a small amount of in-game currency called Kina, so you can check the preview before clearing your inventory.
Extraction rewards include upgrade materials such as Enhancement Stones, as well as the appearance of the extracted gear. This allows old equipment to be used both for obtaining materials and retaining its cosmetic look; the specific items received are subject to what is displayed in the extraction menu.