This is an adapter to let you use a lamp shade harp on your Ikea Symfonisk. To not stress the PLA, I bent the harp just enough so that's it's just snug in the adapter. The collars on the harp aren't utilized.
It required only a little downward pressure to lock in place; I wouldn't use too much pressure and risk breaking the tabs on the adapter.
In the picture I'm using a 6" harp. The lamp shade has an 8" top diameter, 8" height, and 10" bottom diameter.