This might be a bit of a lofty statement but here goes: RAB’s Strata Flex jacket revolutionized how I layer. In situations where I’d previously wear a fleece mid-layer with a light softshell, I could now wear just the Strata Flex. Instead of bringing a lighter piece for that two-hour-uphill approach, I now wear this jacket, and just throw my softshell on over it at the base of the climb.
It is so incredibly breathable I’ve comfortably worn it to +5C, while at the same time I use it as an insulating mid-layer at -25C, and stand-alone it’ll comfortably keep you warm in the mid-negative-teens. It also stretches, a lot, so you can easily perform that weird-upside-down-dance we call drytooling without it coming untucked from a harness. It really is this good and I honestly cannot find a single thing I’d change about the Strata Flex: it’s perfect.
The Strata Flex uses Polartec Alpha 60g/m for insulation, protected by a Pertex Microlight outer, and pairs it with Polartec Power Stretch under the arms and sides of the torso for extra stretch and breathability. Alpha is a knit insulation that was originally developed for the US Special Operations Command but has trickled down to the retail consumer. This construction method is less prone to coming apart than traditional synthetics and thereby allows the use of much more air permeable inner and outer fabrics that increase breathability. At the same time, Alpha retains heat very well, achieving the Holy Grail of synthetic insulation: breathability with warmth.
The Pertex Microlight outer repels light rain or snow, and effectively blocks wind gusts. Worn as a mid-layer, the slick outer slides easily under other layers. The underarm and torso side panels add to the jacket’s breathability. The cuffs, with low-profile thumb-loops, are also made of Polartec’s Power Stretch for a soft, comfortable next-to-skin feel. But the standout really is the Polartec Alpha insualtion.
Fit is, and I’m going to use that word again, perfect. The hem is long, and combined with the stretchy fabrics, stays tucked in under a harness. The sleeves are long enough to keep your wrists covered, even without using the thumb-loops. Cut through the torso is slim, the neck opening is just right and is lined with soft fleece for comfort.
I even like the two hand pockets which are big and lined with soft, cozy fleece, and have unobtrusive yet functional zippers. They’re great at keeping your hands warm on cold approaches but at the same time the zippers don’t annoy or interfere when the jacket is tucked into a harness. There is no chest pocket, or inside pockets, but as the jacket stays zipped up most of the time when I’m wearing it, I don’t even miss these!
Not sure what else to mention… performance and fit are exceptional, and the attention to detail is impeccable. I honestly do think this is the best active-insulated jacket I’ve ever used, and I’ve worn it more often during the past winter and shoulder season months than any other piece I have. I only wish I had a second one!
The Strata Flex is absolutely phenomenal, and by far the most versatile piece I’ve used in the mountains. Seriously, get this jacket. It’s not just good, it’s perfect.
Pros: breathability, insulation, stretch, fit, ie. everything
Overall: The best active-use insulated layer out there.
RAB provided The Alpine Start with a product sample, but this in no way influences our opinion.