Ultra-thin, compact dolly (with casters on the bottom). I was using it for under-bed storage. It also fits under sofas. Can be connected both vertically and horizontally. Selling all three together. Width: 40cm, Depth: 27.5cm, Height: 3.8cm Reference: https://www.amazon.co.jp/dp/B0CM2XVWDW?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1 A new one seems to be 2,080 yen each on Amazon. *The box in the photo is just a cardboard box and is not an included accessory.