FKNA from Russian Federation, Public Profile

Perfect piece for active moving, sheds wind, snow and some water. Rab's STS Matrix material is uber-durable, it is very thin, silky smooth and stretchy and can be worn right next to your skin, but at the same time uber-durable: one of the best fabrics I've ever worn, really. Handjamming in the granite cracks, rusty ski edges, all combinations of rough velcro-buckle hot spots ... no SIGNS (!). For the prev version of Borealis (known as Boreas) the seams was the weak spot, as there were exposed and peeled immediately, but seams are all hidden in the current gen Borealis.
The only thing I can mention now: the color of the fabric faded noticeably on shoulders after two seasons of active use.
Cut is nice, more arcteryx'y than typical american, long sleeves broad shoulders&chest, true waist size.
Personally more often prefer pull-on version as more hardcore and technical combo of base layer and windshell.
Jacket version is more of a "jacket" with almost the same functionality.
Essential piece of my wardrobe all year round.

Great concept, materials and craftsmanship.
But the construction and geometry is really questionable.Thanks for your mail and feedback.
1) Geometry. The back length of the pack is made noticeably shorter than your conventional pack,
and it is intentional (asked Exped people):
"It is correct that the Serac 35 in backlength M is rather on the short side of things what the torso length is concerned, but please be aware that this is a highly technical alpine backpack which is carried "high" in order to make sure that there is access to the climbing harness at all times (when backpack is on your back). When you have a look at the attached photo you also will see that the waist strap angles slightly downwards, so that part of that shorter torso length gets compensated when you tighten up the waist strap"
It may be OK for smaller super-light summit pack, but didn't work for 35L technical ski pack.
When fully loaded + the skis strapped on it is PITA to carry Serac, as either it sits too low and tends to recline you back, or there is no way to use waistbelt correctly to transfer the load on your hips.

2)Small features like internal pocket (which is become unusable if there are shovelhandle&probe attached), shovel handle&probe attachment points (really hard to put it back it the pack is stuffed), shovel pocket (really small and will not fit big shovels)

So as the shorter backlength is not a bug but the feature, it is not mentioned anywhere in description of Serac, and it was big