Bottle Transfer Connector Cap for 25mm OD neck - Hand Cream, Shampoo, Body Wash

A scaled-down version of the original.

Many bathroom products come with pumps to extract the bottle contents, but the tubes on the bottom of the pumps don't reach all the way to the bottom of the bottle. Thus, after the pump stops pumping, there can still be a significant amount of product still in the bottle. Rather than throw that out, people transfer the remainder into a second bottle of the same product. 

These types of connectors make that transfer much easier.