How can I check if a Rocket League item can be used in Fortnite?

You can check if a Rocket League item can be used in Fortnite by going to your garage and checking if there is a Fortnite icon. Next to the icon will say "Buying this item will also make it available in Fortnite." If no Fortnite icon is visible, the item is not available in Fortnite. Bundles in the item shop will also display if the same icon.