Yes, it is the missing part of our Ikea Poang chair, that we have tried to pick up twice before, and both times ended up with the wrong part. But not this time!
Consequently, one of the first tasks I did the day after we got back from our trip, was finally complete the Poang. It couldn't have come at a better time. That chair is the only one I can stand to sit in for more than 20 minutes without having to re-adjust or developing butt/back pain. Ikea for the win!