I bought the x-small which goes up to 23" waist for my daughter who has a waist of 22" and the x-small just fits her (no room to grow). So much for growing into it with an inch to spare.
The build quality is very cheaply made. In terms of performance, my 'princess' did not complain when wearing it so I will take that as no issues with comfort and fit.
The product does the job but I question its long term durability. To be honest, if I had to provide an educated guess the manufacture did that purposely because they figured the child will outgrow the fit before the product wear becomes unusable.
The positive is the adjustable length feature using velcro straps.