I'm a size 10 and 5'4, so fitting the latter end of the scale on the sizing recommendation. I took my chances with the size Small and it fits perfectly, it's a little tighter on the sleeve tips by the wrists than the rest of the piece but it's not a major issue for me. The material is thick but stretchy, soft and breathable, so the fit is entirely what I wanted. This is amazing for my cold early morning walks and jogs so I can't wait to get use out of it.
Main takeaway - it is a slim fit; tight on the sleeve tip but not so tight it is uncomfortable because it's still overall stretchy and breathable. You can feel the quality in this hoodie, worth the price in my opinion.