This is a bottle-thread adapter that allows a fitting designed for one thread size to be attached to a bottle having threads of a different size. I made this adapter so that I could attach a pump dispenser from a Costco shampoo bottle to a bottle of liquid hand soap that has larger threads.

This adapter has, on one side, female PCF38P4 threads, and, on the other side, male M28SP415 threads.

The SolidWorks file can be found in the github repository for this project.