We recently bought a second-hand Quinny (tm) baby carrier on the cheap. Fortunately for me, a single plastic part was missing.. :-) So I decided to copy its mirror counterpart. It's not completely finished yet, but it works on our carrier, so I decided to upload the design. I'm planning on finishing it at some point.print the three parts (with support, or enable the manual support in the source code)sand the small part slightly where it will touch the aluminum bar (this step may not be necessary)connect the main two parts with a long M5 bolt (this may require a bit more sanding, as I made them fit too tightly probably), to check everything fits and moves smoothly.remove bolt again, attach inner large part to carrier, insert the small part, then the outer large part, then put in the bolt again.