I want to store some data in an ItemStack. What I want is that when a player r-clicks with this item a certain command will run. The arguments are displayed on the lore of the item. But I don't really want to extract the data for the command from the lore. I've tried creating my own MetaData, but this is has no access modifier, so I can't use it. When extending an existing MetaData class (like CraftMetaBook) it will throw an error when giving the metaData to an ItemStack. Because my class is not CraftMetaData.class... The same error when using MaterialData. I've also tried using a custom Enchantment, but the data is instantly lost. Is there a way to store custom data without using NMS?