Koyal Wholesale 5" Natural Birch Bark Cube Vase, 12-Pack Sold in Pack of 12. Each wooden cube bark vase measures 5" L x 5" W x 5" H. Birch bark lines the outer portion of the square pot vase, while a smooth wooden shell lines the inner portion. As these wooden cube vases are not waterproof, the addition of plastic lining is highly recommended for any flower arrangements requiring water. Due to the lightweight nature of these birch bark covered vases, weighing the vase down with stones to prevent heavier arrangements from tipping over is suggested.