I bought this in a much bigger size than I usually wear, because I need stuff to go over my airbag vest.
The arm adjusters mean it isn't flapping around (despite being bigger than I need), and it's so well ventilated. It got a bit damp when it rained on me, but dried out quicker than I thought it would - Thought with it being cotton it would be a nightmare but it wasn't.
My only ask would be for velcro at the end of the arm zips, so I can unzip for even more air, but have the wrists done up which I prefer (in the hope that if I do come off, they won't just slide up my arms).