Creative Block of Diamond Barrel
From Feed The Beast Wiki
The creative block diamond barrel is an item from the Factorization. Intentionally created for mapmakers, it can also be spawned in via commands or NEI. It is much like a regular barrel, right-click with current item in hand to put in, but when left-clicked, it spews out an a stack of that item (if the item is NOT stackable, only one of the item will be dropped) and keeps the item locked into the barrel. The only way to change the item set into the barrel is to right-click another item into it.