Bottle coupling/draining device

When employing viscous liquids dispensed from bottles I don't like waiting for the contents of nearly empty bottle to drain to the neck end before they can be used. To avoid this I will drain the dregs from nearly empty bottles into new (so nearly full) bottles. It takes some time for viscous liquids to fully drain from the nearly empty bottle so I made a coupler that allows me to join the two bottles together (with the nearly empty one uppermost) and so leave them unattended, coupled while the one fully drains into the other (usually overnight).

The internal shape of the coupler is a little funnel-like, in that it has a nozzle on one side (the side that should be down-most during draining). The diameter and thread size seem to be common to many bottles.

When printing this I had trouble with adhesion to the print bed, so I modified the design with an inner ring that increased the bed contact area and solved that problem but needed to be cut off after printing. I have included that model (with the bed adhesion ring) and the same model without the ring (the file names indicate which is which).

The threads work best if printed at relatively low layer heights, I used 0.1mm. No support material is necessary to print this.