A couple of times now, I've seen discussions around the topic of creating tubular shapes that have one profile on one end, and another profile on the other end.

These things are a couple of examples of creating such things.

It's a work in progress, but it's a fairly straight forward process. I think this technique can be used to create things like frosting heads, or sugar cookie templates.

It's still a work in progress because when I generate the shape in Banate CAD, the face normals are turned the wrong way, so I use Mesh Lab to flip them after the .stl is generated.

If they could be mated to something with threads on it, you could imagine making hose attachments fairly easily. Also good for mating differently shaped things, like square tubes to round tubes.

1) Download
2) Print
3) Fiddle About
4) Rejoice!