George Cave

Suppose you wanted the perfect new insulating mid-layer. A jacket which was warm and breathable, but also gave you the flexibility to stretch and move as you wished. Would you end up with the Rab Strata Flex?

Rab’s new jacket joins an existing family of two Strata products: the Strata Hoodie and Strata Vest. Like its brothers it features Polartec Alpha as an insulating material but the key distinction here is that this is a hybrid. The Polartec Alpha might be there to keep you warm but stretch panels run up the insides of the arms, theoretically offering a much more liberating sense of movement than an all-out synthetic jacket.

I will come to how the jacket fared shortly, but first it’s important to address a glaringly obvious issue with this top. The Strata Flex has no hood, and it needs one. I found it downright bizarre that Rab chose not to bother and after several months of use I’ve yet to come up with a good reason for its omission. A mid-layer might be designed for the “middle” but I would start, end and often spend much of the day wearing nothing but this jacket and a baselayer. I appreciate there are schools of thought who prefer to wear hats and keep the neck uncluttered but Rab wanted to design a jacket “for alpine climbing and fast-moving outdoor activities”. In my book the lack of a snug fitting hood is a significant mark against this product’s desire to be an all-round insulating mountain mid-layer.

“The Strata Flex has no hood, and it needs one.”

Performance

Wearing the Strata Flex feels a little like wearing a cross between a cheap synthetic sleeping bag and a nice soft fleece. Polartec Power Stretch which forms the side panels is a super stretchy wicking fabric which feels great on the skin here with its soft internal face. The panels start at the waist and run right up the inside of the body and down the arms. The rest of the jacket is constructed from Polartec Alpha, a fabric which can be simplistically described as a less warm but more breathable competitor to Primaloft. The Alpha is covered on the outside in Pertex Microlight which has a nice matte texture whilst the inside is a thin mesh. The blue colour is lovely but there’s also a black model if you prefer.

After a winter and spring of climbing and ski touring, I’ve come to conclude that for general all-day mountaineering in colder weather the level of insulation provided by the Strata Flex is spot on. It was too much on the warmest days in the sun, to the level of being a bit clingy when sweaty, but throughout the colder UK winter I was invariably warm and never felt clammy inside. In particular, I found it very easy to regulate how warm I was on an approach with a quick opening of the zip and if I needed further layers the jacket’s low-bulk means that outer garments slip over well. There’s a definite sweet-spot when it comes to balancing warmth, breathability and windproofing and this jacket hit that target well.

The only negative was that I was actually surprised how much I felt a noticeable difference between the two fabrics. When the wind picked up there could be a definite passing chill in the under-arm areas. It’s a little harder to assess how much more restrictive the jacket would have felt if made solely from the synthetic insulation but Rab have gotten away with a very close fit all over. I reckon their marketing tagline of “extremely high levels of freedom of movement” stood up well to scrutiny.

“I’ve come to conclude that for general all-day mountaineering in colder weather the level of insulation provided by the Strata Flex is spot on.”