This is an extension box for a Japanese honeybee stackable hive, with knots and cracks. It is for Honey's House and Honey's Mansion. Japanese honeybees prefer weathered boxes, so professionals sometimes prepare them a year in advance. The dimensions are 33cm x 33cm outside, 27cm x 27cm inside, and 15cm high. The thickness is 3cm, providing a comfortable environment for the summer heat and winter cold. The comb support rods are shaved to 8mm. There are various ways to install the support rods, such as cross-shaped or well-shaped, but bees dislike too many, so we use two parallel rods. Therefore, when adding extension boxes, if the support rods of the lower box are horizontal, set the support rods of the upper box vertically. This provides an effect similar to a well shape with fewer rods. During the honey harvesting season, the hive should be four or five tiers high, so one of them will be supporting the comb, and the comb will not fall even if the upper tier is cut. If you are using this for other hives, please be sure to understand the dimensions before purchasing. Please note that this is handmade, so there may be deviations of approximately ±2mm and deviations due to wood expansion and contraction. By the way, if the colony grows strongly, we stack up to 5 or 6 tiers including the entrance box in the fall, so we recommend that those who have a Honey's series set purchase an additional 2 or 3 boxes.