These are Honeycomb Spider Hides which can be magnetically fixed anywhere inside an enclosure.
Simply peel off the white backing on the second magnet and stick it in place where you wish, on a clean dry surface.
You then attach the hide onto the magnet that is stuck in place.
It can be removed and relocated, by simply peeling the fixed magnet off slowly and reattaching again on a clean dry surface.
This listing is for Black.
They measure 25mm wide by 30mm deep. 2mm thick walls.