To list more than one item on a single listing, the listing’s condition must set to Brand New. If your items are not brand new, separate listings must be created for each unique item.
After selecting Brand New as the condition, scroll down until you see “Inventory”.
Select “I have more than one”.
From there, a new field will appear in which you can specify the quantity you are selling.
Please note: If you are not an authorized dealer, you cannot list brand new unless you handmade the item yourself. If you are reselling a piece of gear that you bought brand new from a retailer—even if it has never been used—it automatically falls under the Mint condition since it may no longer be covered by the manufacturer’s original warranty.