This is a plug to hold the 20mm air valve of the floor of an Intex Explorer 2 kayak open while you fold it up for packing. I found that while I was packing the kayak away after use the valve would close and air would remain trapped in the floor making it too bulky for the bag.

The idea is that it is short enough to leave in after packing without damaging the kayak, as you fold the kayak up all of the air in the floor is expelled. It should work on anything inflatable with a 20mm number 3 air valve.