I purchased this cosplay (the len version) for my friend. They got a medium, and amazingly it fit really well! They even recorded a dance cover in it without any trouble, meaning they could move really smoothly in it!
Unfortunately, the ribbon around the socks didn’t stretch at all so they couldn’t fit it around their calves, so we had to replace them, and some of the buttons came loose when they first put it on, but overall still really happy about it!