I ordered an S initially. Although it fit well for my build (172cm & 59kg), it has little space for adding extra layers in the middle. That's why I returned it in exchange for an M. Having wait for about a month (I am from Hong Kong), the exchange arrived earlier this week, and I just couldn't wait to have a try. And I was just absolutely pleased with this outer shelter for three reasons. Firstly, I felt neither wet nor cold after riding in the winter downpour (winter is cold & wet here) for a couple of hours, and I could tell that was what insulation means. Secondly, I appeared glowing even without any street light, thanks to the neon yellow colour. Finally, the zipper openings offered perfect & easily adjustable ventilation anytime. However, I did not try putting the hood over the helmet as I preferred using a waterproof helmet cover (also by Showerspass). Should there be a child version for this jacket, I would definitely buy it for my children too!