I use the WALI mounting system to hold up VESA monitors and other items attached to the main mounting post. In this case I have a large microphone used for voice overs and streaming and it's attached to a typical "lamp arm" style of mount with a desk clamp on one end. I wanted to remove the arm from that clamp and just insert it into the top of the main WALI support post and to do that I needed an adapter.

Normally there's a plastic "plug" that fits in the end of the WALI support pipe; this adapter replaces that. You'll notice it had a notch out of one side; that's to accommodate a weld that runs down the inside of the WALI pipe.

My mic boom has a 13mm wide pin that normally goes into the desk clamp and so my adapter plug has a 13mm wide hole in the middle where the boom pin is inserted. This works fantastically well - there is more than enough structural support given a dense print with strong walls and the boom moves easily side to side as needed.

I printed this in PETG but I see no reason that PLA wouldn't work just as well.