I'm new to selling on vinted...
Anyway I've sold an item that is very lightweight, so I went with the "small" parcel option.
However, I've realised it could do with going in a box to avoid getting squashed.
Have looked at the in post instructions which seem to suggest you can change to a medium locker when dropping off, but won't this mean it's been underpaid? It doesn't give dimensions on vinted only weight.