In regards to sizing for us smaller dudes i sized down from my normal small. For reference I’m 5’7 and 147lbs and wear a small in the N1 and M65. I was a bit worried with going with an XS but I trusted the measurements and everything worked out. Even with it being an XS it feels looser than the N1 in a small. A medium weight hoody or flannel fits fine under it with just a bit of tightness in the shoulders. I’m in love with this jacket