The Item Box Transfer is a team action that certain racing cars can pull off. With it, a car racer can request or offer an Item Box power-up to their teammates to help themselves or their teammates out throughout the race.
In gameplay, if the player has a Wisp they want to transfer to a teammate, they can press the item transfer button (//) to offer their Item Box to a teammate. A prompt will then appear at the top of their teammate's screen saying they are offering an item. If a teammate responds by pressing the item transfer button back (//), they will receive the Item Box from the offering playable character. After the transfer process, the receiver can receive three of that Wisp even if the sender only had one, although this does not apply to the more powerful Wisps such as the Yellow Wisp.
Additionally, If a player needs an Item Box but are not being offered one, they can press the item transfer button to send a request to their teammates. If a teammate with an item responds by pressing the item transfer button back, they will send their item to he requesting teammate. Also, pulling off the Item Box Transfer will charge both the player's Ultimate Meter and their teammates'.