I've made these POD cubes to to in the sump to house PODs for those without a fuge. The idea is for the PODs to live within the cube and reproduce. Once or twice a week, the cube is removed and either placed in the DT overnight and back in the simp or just get shaken in the TD and straight back into the sump. The top and bottom floors have no direct openings which will allow some PODs to remain in the cube for further reproduction. All floors and hallways are all interconnected to allow for free movement anywhere within the cube. The cube measures 3-7/8 square and the hallway openings are around 1/4" square. Every hallway has an intersection hallway at its center and there's a shaft that goes from the every bottom to top floor. The cubes are also designed to be stackable with 4 holes at the bottom to align with the 4 small dots at the top. Obviously they don't need to stack but the option is there.I'm selling these for $28 shipped within the lower 48 states. Discounts will be given for orders of 2 or more cubes. Please PM me with any questions. Thanks.