This jacket will fit fairly snug. There seems to be a bit of room for layering but not a ton of room. In my experience when manufacturers say "performance" fit they mean that they expect you to be working harder than the average joe so you don't need quite as much layering but that's just what I've seen. Hope that helps.I'm usually a Large in jackets, sometimes an XL, and on this jacket the Large was just too snug a fit that I wouldn't be able to layer well and it was a bit too snug around the ski pants. I am ordering an XL.