Size: should I size up from the american brands (I wear L in OR, Marmot, MH etc).

Size down. I'm 6'2", 40" chest. I tried the large, and even with a heavy fleece on, it still left enough room underneath for a whole ski patrol dog!

I'm 6' 175 lbs, 41" chest and 35" arms. For jackets I prefer to wear medium in Arc'teryx, Patagonia, Norrona, Berghaus, MH. Large in Rab and Mammut. I have large in Cloudveil and Marmot too, but albeit I use these in sitiations where I want a baggier fit (skiing). I'm a backpacker/alpinist. I will carry this beauty for most trips into the White Mountains of NH where the weather is often fickle and dangerous. (I have not actually worn it in action yet, but I am a gear whore with experience and know a good jacket when I wear it anywhere). I just received this jacket in both black Small (!!) and Morrocan Blue Medium. Both fit well, believe it or not. I prefer a streamlined fit rather than boxy, but do like to have room for a thin base (always), mid-layer fleece/softshell etc (occasionally) and rarely in very cold weather a micro-puff or down sweater with (or in place of) the fleece. I've tried all these combos with both S and M sizes. Believe it or not the small fits decent - still freedom of movement and I don't look like a stuffed sausage. The medium obviouly has more room, but not very noticiably so. The length of the jacket and arms are not substantially different enough between sizes to swing the vote, but the small was slightly shorter (just below the belt in the front, a few inches longer in the rear. In extreme weather I wear bibs anyway). As I mentioned I prefer a more svelt fit, as during 70% of the conditions for use I won't be heavily layered, and a tighter fit generally breathes better. When I am layered down, mobility is usually less of a concern. Bottom line, both would work but for the first time in many years I'll be wearing a small. This is a generoulsy sized jacket! My recommendation is not to be affraid to size down if you are borderline between sizes. If you can afford to try various sizes, definitely do so as tastes may vary. Apparently Montane re-sized their cuts for this particular jacket recently (late '09 or so) so beware! This is a beautiful jacket. Well made, good looking and well configured. Buy with confidence. Bring more Montane to the US. PS. their customer service is awesome. Pick up the phone and call them! They were very helpful.

It depends what you intend to wear under it. I usually wear a medium, and a medium super-fly xt fits comfortably over a bulky down jacket (and then some). Other pages I have read suggest that the super-fly xt is cut extra large for this very purpose (this may be why Big Jim recommends sizing up--perhaps his experience is with a different Montane jacket). Without a bulky mid layer, there's a lot of room in there (I can wear a medium-sized, medium-packed daypack under it and still zip it up), but the drawstring at the lumbar helps tighten it down (even if it does make me look like I'm wearing a bustle, ha!). If you don't plan on wearing anything bulky under it, I might suggest sizing DOWN.

ive just been in contact with montane and the xt is still currently generously sized/about one size bigger than their other hardshells, the xl is about a 45 inch chest but all other montane hardshells are 42 inch chest in the large size. i just got the montane halo jacket and the large is too small for me as i have a 43 inch chest but the superfly xt large is a good fit as its closer to a 44-45 inch chest fit. i have a large in a marmot jacket and fit north face large so i would say get a large in the superfly xt but if your considering any other montane clothing you probably want the extralarge

i have a 2007 superfly xt, im 6 foot, 43 inch chest, fit north face large perfectly. sizing is odd with montane, the superfly in xl was too big but the large was exactly right however all other montane underclothing i need an xl in so i think they made the 2007 sperfly xt a generous large for layering, i dont know if they still have the generous one size bigger in their hardshells than the rest of their clothing though.

Size up... I wear large in most everything and the Montane jacket I own fits very trim in XL.