I bought these shoe trees in a size small, which is marked as fitting women's 5-8.5 shoes, to keep a pair of size 5.5 penny loafers in good shape. The second time I inserted these into the pair of shoes, they ripped the stitching on the toe of one of my shoes, ruining them! Clearly the trees are way too big for a size 5.5 shoe if they're actually ripping out the stitching. I wouldn't try these trees in anything smaller than a 6.5, unless the shoe is particularly sturdy and has no stitching around the front.
I'm very dissatisfied, as these ruined a brand new pair of shoes that otherwise would have lasted 5+ years. If you wear a women's size 5-6, do not buy these! Save your money and stuff your shoes with newsprint instead....