A hook for hanging the stroller seat! 
It’s designed to work with the Bugaboo Donkey 5 seat, but may work with others to. Bugaboo Fox 3 confirmed!
Comment if you have confirmed another model of seat.

The hook is reversible in Bambu Studio, so if you want the seat facing right, mirror it in the slicer. (Y-axis when i checked)

There is also a little notch for one-handed hanging, making it easier and you won’t get your fingers stuck on the bar. Scoop it up and hang it wherever you please!

Printed large face down without supports, it may give you a warning but it printed fine in PLA Basic for me. 3 walls feel sturdy but you increase/decrease as you wish!