My wife wears a size 6 shoe, (she prefers wearing ‘normal’ leather ankle boots when on the bike). I bought the over-boots to cover my cycle shoes which are a 10, but they fit over her boots really well.
I guess that’s the beauty of neoprene.
I’ll check if they have a size on them somewhere, (though it won’t be for a few days).
They did a great job of keeping her toes warm & dry, and as you say, are a doddle to slip on, are okay for walking in, and so discreet (in black anyhow) that they’re barely noticeable.