Question regarding shipping rooftop bike trays

[phoenix]

I have two NIB Thule Circuit bike carriers I want to sell. I want to offer them for sale in our Classified section, however I’m wondering about shipping.

Does anyone know if I can just slap a shipping label onto the original box and call it good? Or, if I sell them both to the same person, can I tape the two boxes together and just attach a shipping label? Or, do they need to go into a separate box for shipping?

I feel like I’ve seen stuff like this ship with a label on the original box.

Any input is appreciated, thanks!