Theoretically this model provides a corner connection for three 16 mm pipes. However, as holes usually shrink for 3D prints, it can be a loose or even tight fit for 15 mm pipes - depending on your printer. So try and measure.
If you have pipes with different diameter, you can proportionally scale this model.
Important: Don't force the pipes into the horizontal holes, as it may force the layers to separate. (Believe me it does, guess how I know that ;-) )
This model has 1.6 mm walls, so if you have a printer with 0.4 mm nozzle, and you set the shell thickness to 0.8 mm in your slicer, then you will get solid walls around the holes.
You can print this model without support, but in that case you will probably have some hanging material within the horizontal holes, where the nozzle printed in the air. That may be okay, depending on your use case. For me it helped to get tight fit for 15 mm pipes.