Questions about Really Useful Box Storage box

This is a 4-piece set.

The stackability of Really Useful boxes depends on their specific dimensions. Here are the relevant dimensions for the 18L and 9L boxes: - The 18L box measures 48 cm x 39 cm x 20 cm. - A typical 9L box measures approximately 14.5 cm x 26 cm x 15.5 cm (or similar dimensions, depending on the model). To place two 9L boxes next to each other on top of an 18L box, the widths and lengths of the 9L boxes would have to match. As the width of the 18 litre box is 39 cm and the width of a 9 litre box is about 26 cm, two 9 litre boxes will fit next to each other in width (26 cm + 26 cm = 52 cm, which is too wide for the 18 litre box). Therefore, the 9L boxes are not dimensioned so that two of them can be stacked next to each other on an 18L box.