Inner covers are essential for wintering bees in wooden hives. An inner cover allows moisture to escape and fresh air to be circulated throughout the hive when properly used with an outer cover. Our "all season" or "winter" inner cover features a rim with round ventiation hole and a deeper rim on one side to allow for feeding patties. Round internal hole accepts a standard mason jar for internal feeding.Made of Luan plywood with a pine rim. Fully assembled.