This is a bracket to allow a computer fan (120mm) to connect to an vent pipe. I use it for a spray booth extraction fan. The vent pipe slips over the bracket which is screwed to the fan's mounting holes.
My printer doesn't allow it to print in 1 piece, so I printed 4 of these and they slotted together (no glue required).
Polymaker Polylite PLA
Depending on your printer, some filing may be required. Otherwise just print 4 of them and slot them together.