These are simple riser hooks to attach to Curver brand storage boxes, specifically their infinity dots range.

These are an affordable & sturdy storage box in the UK, found in many shops (mine came from B&Q) and they were £2.50 each.

These are the 4.5l boxes.

I use mine on the desk for working through printed items but it's better that the footprint is now minimised greatly.

Designed with wide feet so that side to side movement doesn't make the box fall in.

They may fit other boxes, the width of the box wall is 2mm & the step down to the lip is 28mm if you want to try.