Great question! The Koala pillow has a label on the side of the cover with an "S" and a "F". The side represented by the "S" is the softer side and the side represented by the "F" is the firmer side.
As our Koala Pillow has a removable cover which you can cold wash, it can be a little tricky to work out which side is which when putting the cover back on. In this case, the big holes indicate the soft side and the smaller holes indicate the firm side!