I followed the advice in the description and bought an XS, a size smaller than I normally wear (S). It was way too small....especially the wrists, I could barely get my hands through them. Otherwise it was a nice jacket.
I bought this jacket expecting an average softshell jacket, warm but breathable. This one is more like a shirt. The material is really thin, and there is no lining. It reminds me more of a windbreaker. Also didn't like the fit, it was really baggy (I ordered a small, which I normally wear).