Few pieces in my kit have been put through such varied and rigorous rotation as this one. In the past few months, I have worn it close to every day — whether in town or on an adventure. The warmth amazed me, and the breathability left me breathless (in a really good way). Arc’teryx nailed the active insulation with this alpine focused hoody. Truthfully, the comfort it provided me on my hiking, climbing, and cold-weather running adventures has put it in a class of its own.

Women’s Arc’teryx Proton FL Hoody Features:

  • Articulated elbows and gusseted underarms for full mobility and comfort
  • Low-profile and helmet compatible adjustable hood
  • Two zippered chest pockets, two zippered hand pockets
  • Octa Loft insulation, providing premier breathability and comfort
  • 9.7 oz (275g)
  • MSRP: $259.00
Review: Arc'teryx Women's Proton FL Hoody

Great collar height and hood.

Proton FL is in a class of it’s own

The Proton FL is designed with a keen attention to alpine needs for long days in the mountains. The airy insulation ensures that you can put it on in the wee hours of an alpine start, and leave it on for the rest of the day. The Proton FL (short for “fast and light”) is a cousin to the Proton LT and AR. Unlike the LT and the AR, the Proton FL is designed to be — you guessed it — fast and light. This means cutting down the weight in areas that it isn’t totally essential, and implementing features that capitalize on maximum impact with minimum weight.

Arc’teryx didn’t just focus on a lightweight product when designing the Proton FL. They were also intent on creating a product that could move, adapt, and protect. When wearing this jacket, I was rarely in a situation that required I take it off. Even when in high-output activity, I found this jacket breathed exceptionally well. While doing a 20 mile day-hike in the North Cascades I spent more of those miles — whether uphill, at elevation, or hiking out — wearing the Proton than miles I spent without. This experience evidenced the impressive versatility of the Proton. Cold morning to high-output activity to high elevation to a nighttime descent? Cool, I’ll wear the Proton the whole time.

Review: Arc'teryx Women's Proton FL Hoody

Relaxing a little mid-hike.

During stop-and-go activity, the Proton FL reigns supreme. The Octa Loft Insulation is intended to create what Arc’teryx calls a “comfortable microclimate.” Basically, wear-all-day comfort that allows you to explore a range of temperatures and output levels without being held back by your gear. I wouldn’t hesitate to grab the Proton FL if I were packing for an alpine trip, but I also wore it while running in Spokane’s winter weather.

Sometimes breathable pieces compromise on warmth — not the Proton FL. While it doesn’t claim to be any kind of heavy insulator or storm-proof shell, it performs perfectly as a weather-resistant mid-layer that doesn’t need to be stripped when weather or output level changes.  Bonus: the lining of the Proton is super-soft and cozy, and feels great against bare arms. But if you find yourself wanting a baselayer underneath, those layers will comfortably fit under it as well.

Review: Arc'teryx Women's Proton FL Hoody

Squeezing in one last climb before the sun goes down. I knew I’d stay warm even when the sun disappeared while wearing the Proton FL.

If I could point out that one thing that I love the most about the Proton FL, it would be wind and water resistance. My trusty Patagonia R1 offeres great warmth and minimal wind resistance and my R1 TechFace cuts down on the warmth and upps the weather resistance. However, the Proton FL meets these midlayers in the middle (get it?). Increased warmth with ample weather protection, without discarding necessary breathability. The Proton FL uses Fortius Air 20 for the shell. Similar to the Fortius 40 used in the Proton LT, the Fortius Air 20 is comprised of a smaller thread, providing increased breathability and overall weight reduction.

Arc’teryx paid close attention to functional details with the Proton FL, choosing to integrate insulation in the areas that it was most necessary and cutting out what may be superfluous. A prime example of this is in the insulation placement in the hood. Instead of having a hood that is fully insulated, the top of the hood is uninsulated. While this might be a point of discomfort for some, I loved this design for a few reasons.

Review: Arc'teryx Women's Proton FL Hoody

Happy hoody-wearer. (Note how the zipper is snagged on the garage about an inch from the top)

The specifically placed insulation cut down on the weight and made wearing a helmet over the hood incredibly comfortable. Since the top was simply Arc’teryx’s weather resistant Fortius Air 20, there was no additional material between my noggin and the helmet. The result? Unbelievable comfort with hood up. The insulation is extended up around the high collar and around to the back of the neck. So with the hood up and the collar fully zipped, I felt that those areas susceptible to the elements (back of the neck, throat, etc.) were warm and toasty. Even if I chose not to have the hood up all the way, the insulation in the collar still ensured that my neck was warm, and didn’t allow any drafts to sneak in.

Review: Arc'teryx Women's Proton FL Hoody

The minimalist hood was totally comfortable under a helmet.

The adjustments on the Proton FL are few. A single toggle on the back of the hood and two on either side of the hem. The cuffs are an amazingly comfortable stretch elastic, and fit so perfectly that I never found myself messing with the cuffs or wishing they were of the velcro variety.

The hem boasts an added tubing to really seal out drafts, while also keeping the jacket secure when worn with a harness. From what I can tell, I believe the material to be some sort of foam. While I liked the fact that it never really rode up, I don’t know that it was entirely attributable to the tubing, which I mostly found somewhat strange and a small bit distracting. Furthermore, I have a very apprehensive relationship with embracing any kind of extra foam simply due to the environmental impacts of the material. That being said, I felt that it wasn’t a totally necessary feature and I’d rather scrap it to save on materials.

Four pockets ensure that you can store — and access — the goods you want all the time. Honestly, the entire front of the jacket is essentially pockets, divided into 4 parts. Wearing a harness? No worries, the Proton FL has 2 stretch woven chest pockets equal in size to the hand pockets. But those hand pockets are extra sweet and soft, lined with an incredible fleece for when you need a quick warm up of your chilly fingers.

Review: Arc'teryx Women's Proton FL Hoody

Fleecy pockets on the Proton FL (featuring my worn out nail polish)

Consistent with my experience with synthetic mid-layers, I found that after near constant wear I simply could not deny or dispel the stink that had embedded itself in the Proton FL. Soon enough, I couldn’t climb in it more than a single day before the stink was apparent. Perhaps there isn’t anything to be done about this, perhaps I’m just an exceptionally stinky person. Who knows. All I can say is that the stink became a sad reality for my Proton jacket in the same way it did for my R1.

Also, the zipper constantly snagged on the elastic garage near the top. Without fail, I was required to do a little finagling to get the zipper completely up. While not a dealbreaker, it was annoying.

The Good

  • Fantastic breathability while maintaining comfortable warmth
  • Hood design is comfortable with a helmet and very minimal
  • Four pockets for easy access — bonus points for the two hand pockets that are fleece lined.

The Bad

  • Bad odor lingers in the synthetic material
  • The zipper constantly gets caught on the zipper garage

The Bottom Line: Arc’teryx Proton FL Hoody

If you are looking for a layer that is well-suited to the varied temperatures typical of alpine climbing, the Proton FL is a fantastic addition to your kit. Warm yet breathable, this layer is appropriate to wear from the time your adventure begins to when you find yourself at the brewery at the end of the day. It is technical and attractive, and a new favorite of mine.

Buy Now: Available at REI

About Author

Bella was born and raised in the Pacific Northwest, and loves exploring it through backpacking, climbing, and camping. Although she adores the Cascades, she dreams of one day living in the desert. She works and guides for Peak 7 Adventures.

Leave A Reply