Summary

If you use pump bottles, you will reach a point where the pump cannot draw up the last bits of the product. You may want to drain the remnants into a new bottle to reduce wastage. With this print, you can couple two bottles together to drain one into the other. This uses the thread from my other design: https://www.thingiverse.com/thing:7232360 So this is for the large pump bottles.

The ridges around the outside give grip and also shows which direction the draining should go. A small breather hole for the receiving bottle helps reduce burping into the donor bottle and improve flow but may cause negative pressure and collapse of the donor. (If you encounter this problem, please let me know.)

A built-in brim of 0.2mm thickness should help it stick to the print bed. That will need to be snipped off with side cutters before use. Or print the one labelled "No Brim" if you have good bed adhesion.