Morning all. I sold an item yesterday (leggings), which came through with a message saying they had let someone buy using a disabled postage method but I could cancel if I wanted. I decided to proceed even though I'd have to go to the Post Office which is why I disabled Royal Mail in the first place.
Anyway, label comes through for a small parcel and it's Large Letter which has just been added to Vinted as an option. The Vinted guidelines for a small parcel I'm sure are for a padded envelope as medium is for items that would go in a shoebox.
I did manage to squeeze them into an A4 envelope and hope for the best but I would advise you to select medium if it's not going to go through a 2.5cm slot!