Is it a 14mm female to 19mm female convertor or is it a 19mm female to 14mm female convertor? Trick question, it's both.
You can do so many things with this conversion piece. You could turn a dedicated rig into a flower pipe or convert your dedicated into the different size that maybe you have a domeless nail that won't fit anything else.
I'm confused too, but it's a handy piece for the exact right situation;)