Stio Fernos Insulated Pant Review

Stio Fernos Insulated Pant Review by Erin Trail The Stio Fernos Insulated Pants are incredibly well designed active insulation for your lower half, featuring warm and functional materials that will keep you warm in a wide variety of winter activities. Details PeakFill™ Active Insulation (50% Polyester, 50% Recycled Polyester, 40g/m2) Shell and Lining: Relance™ Primeflex,…

Erin Trail

December 17, 2025

5–7 minutes

active insulation, active wear, midlayer, pants, stio, winter, winter pants

Stio Fernos Insulated Pant

Review by Erin Trail

The Stio Fernos Insulated Pants are incredibly well designed active insulation for your lower half, featuring warm and functional materials that will keep you warm in a wide variety of winter activities.

Details

PeakFill™ Active Insulation (50% Polyester, 50% Recycled Polyester, 40g/m2)
Shell and Lining: Relance™ Primeflex, 50 Denier Microfiber Mechanical Stretch Plainweave, 100% Polyester, 94g/m2 with a PFAS-Free DWR Finish
Water-repellent finish resists water and reduces dry time
Articulated knees and action gusset for full range of motion

Encased elastic waistband with drawcord
Three Pockets (hip drop in hand pockets + YKK® zippered thigh pocket

Detailed Review

The Stio Fernos Insulated Pants are everything I’d hope they would be: warm and comfy pants for a variety of cold weather activities.

I am a women’s size medium on the Stio website and the Stio Fernos Insulated Pants fit true to size. They have a jogger style fit and feel, hitting the sweet spot between tight and roomy. I am comfortable wearing them alone or with a layer underneath (fuzzy running tights or wool base layers).

I’ve worn the Stio Fernos Insulated Pant on several cold weather outings:

Casual walking / exploring (craft fairs, holiday light displays, winter ski expos)
Skiing, as a mid layer (under a shell)

I also have them in mind for an outer layer for fat biking, but Colorado has been unusually warm and dry.

The Stio Fernos Insulated Pants have been a great outer layer for winter outings when temperatures dip below freezing. The hand drop in pockets on each hip offer comfortable and natural hand placement. The zippered thigh pocket is very generous, with plenty of room for your phone or snacks.

The Stio Fernos Insulated Pant are built to move. The Relance™ Primeflex fabric (that comprises both the inside and outside of the pants) has a nice stretch to them and has a matte, brushed treatment that feels good on your skin. The PFAS free DWR water-repellent coating means that the pants can be used as outerwear, keeping you dry and protected. The knees are articulated, the side of the upper leg have a built-in stretchy panel, and the pants as a whole are built for full range of motion, making them a great option as an active layer.

I have only had one day skiing under me at the time of this review. I have a few different brands of ski outwear for testing, all shell styles. This is my first season wearing shells (I’ve only worn insulated ski gear before). While I had the Stio Fernos Insulated Pants planned more for fat biking, I learned that they really shine as a mid layer for skiing. They are warm without feeling bulky. They moved incredibly well during my ski laps. AND they didn’t create any discomfort when I tucked them into my ski boots. (note: Stio also offers a knicker length for those who don’t want the extra layer inside their ski boot). I wore the Stio Fernos Insulated Pant with a merino wool base layer and my legs were the perfect temperature all day (my toes were freezing and my upper body, in non-Stio mid layers, was chilly). As a bonus: if you want to ditch the shell for apres hanging out, the Stio Fernos Insulated Pant looks great.

My other days in the Stio Fernos Insulated Pants were light on activity, but typically are the kinds of outings where I get super cold. The pants did wonderfully on a cold and windy evening outing to see holiday lights (the kind where you bundle up, drink hot chocolate, and hope for the best). The biting wind never came through the pants and I was warm and comfy all evening. I could see the Stio Fernos Insulated Pant being great as an option for outside sports spectating as well.

Closing Thoughts

The Stio Fernos Insulated Pants are the “do it all” winter activity pants, do to the purpose built but also stylish design. These pants are made to move and keep you warm, making them a solid option for winter activities (snowshoeing, hiking, nordic skiing, biking, skiing). They also are equally set up for more casual outings due to their warmth and jogger styling.

The Stio Fernos Insulated Pants are available in both pants and knicker options for men and women.

Erin Trail

Trail Boss of Stoke

Erin Trail’s hobby is collecting hobbies. She’s a 5th Generation Coloradan and grew up exploring the outdoors on family camping trips and hikes. Her first backpacking trip was at eight years old to Grizzly Reservoir – she proudly carried all of her own gear those 3 miles from the main parking lot to the Reservoir.

Erin is an adult-onset athlete who started as a Masters Swimmer and then developed into a triathlete. She has completed 5 Ironman races and nearly 20 x 70.3 distance Ironman races, including the World Championship in Lahti, Finland, in 2023. In 2025, she raced for Team USA in Pontevedra, Spain for the World Triathlon Cross Tri World Championship. She placed 9th in her age group and was the 1st American woman in her age group.

Erin Trail on her mountain bike at the World Tri Cross Triathlon World Championship race

Erin Trail on her running at the World Tri Cross Triathlon World Championship race

Somewhere along her triathlon journey, she picked up deep love of cycling. Cycling encouraged her to see landscapes in a new way, learn new skills and to develop self reliance; now she often goes and does Type 2 rides just to see if she can do it. She’s got all the bikes: gravel, mountain, fat bike, time trial and road.

She is even known to combine her love of camping and cycling and go off on solo 24 hour overnight bikepacking trips in the mountains of Colorado. In addition to bikes, she teaches yoga, lifts weights, skis, SUPs and has recently purchased a campervan.

Erin is a former Montana park ranger with a degree in environmental engineering. She loves getting into technical details while putting her gear (and herself) through the paces. She shares her home in Colorado with her husband, Will, and her 3 cats (Zipper, Brewtus, and Simcoe).

Fall and winter 2025 will bring Erin to the “Adventure Side”, with many camping, vanlife, bikepacking, and mountain bike rides. Once the snow flies, she can be find resort skiing, fat biking, and triathlon training (inside and outside).

2026 will bring a National Championship Cross Tri race, a National Championship Road Sprint and Olympic Distance race, and hopefully a chance to represent Team USA once again in 2027 in Edmonton, Canada. She’ll also save lots of room for adventure time with her friends and husband.

When not adventuring, she can be found on a sunny patio somewhere, drinking beers with her husband.

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