Metaboxial Space in Best's Cosmoline is the end of Best's Cosmoline and is an endless plane of Boxes scattered around. It stretches across all dimensions except up. Barely any entities can be here, since most of them share the same limit of not exiting their local box. It follows the same size rule as the Super Fruit, being larger than CAI through Proof by Contradiction.
Nothing can be beyond the Metaboxial Space in Best's Cosmoline, anything beyond it except Alphasm's mind and anything not in Best's Cosmoline IS Metaboxial Space.