3" x 1/2" Spears Pipe increaser/decreaser
These are used to build a light tower stand. This brand is used becuase local brands would not slide over a 1-1/4" pipe. Here is a link to show how to build them.
https://www.youtube.com/watch?v=EwJD-dMAiG4
P.S. In between 2 of these fittngs, I recommend putting a piece of 1-1/2" pvc pipe in between these 2 coupling.