This was designed to be mounted in a boat to support poles for a canopy or a fishing rod holder. The I/D of the inside is 1 9/16" to fit a 1 1/2" post with ease, though it can be scaled to whatever dimensions are needed. I made this in 2 parts that screw together because of the printing size limitations of my printer are smaller than the desired size of the holder. There is a bottom that will stop the pole and hold it at that height, that also has a drain hole printed. A fitting could be attached to the drain hole to guide water through a hose to wherever you would like. The bottom could be simply unscrewed if you wanted a pole to extend further.
The .stl file for the top also has supports for printing the overhang. My printer printed it perfectly with only the support in the file, so nothing further should need to be done other than print it.