Hi! If it's of any help this is my RMC J100, Im 173cm, slim build and wear a size 38. I think the fit is spot on if I wear only a shirt or a very thin layer underneath, the moment I add a hoodie or something heavier it gets a bit restrictive, but as some people here have mentioned it is kind of a trade-off. You would probably fall into a range of sizes so it is a matter of making sure what season (or seasons) you want your jacket for, and also how you like the fit aesthetically. I could use a 40 for sure, but then it would get a bit too long for my taste and probably would look a bit too oversized on me, and because I like this style of jacket to look slim I went for the smaller option, but again it all comes to your preferences. One thing I can say for sure: it is an amazing jacket! You won't regret it