The Proton FL is unlike any other insulation piece in Arx’teryx lineup. I’ve had the opportunity to put my jacket to the test this year from crossing Iceland, to climbing mountains in the rockies, to trekking along the east coast trail. Here’s what I think about it.
Many years ago the military demanded a more robust insulation. Something that could effectively replace the natural insulator, down. They needed something that stays warm when wet, dries out fast, and keep its’ warming properties over prolonged abuse. That’s how synthetic insulation was born.
Every year there’s marginal improvements for synthetic fibre insulation. Making small adjustments and creating a more effective warmth to wait ratio. A ratio that down insulation still rules over.
Arc’teryx’ newest fast & light jacket in the Proton series closes that gap. The new Octa insulation was used in my favourite running jacket, the argus for men and gaea for women. I know the insulation is crazy breathable and super warm in the endorphin jackets. I knew I could expect the same performance from the comparable Proton FL jacket.
The Proton FL is the answer to 4 season layering. The jacket weighs only 320 grams, making it just slightly heavier than the comparable Atom SL jacket. The Proton FL has a few new features making it a little bit warmer and and even more versatile than the Atom SL.
The octa insulation is distributed evenly throughout the jacket, including side pannels unlike the fleece side panels found in the Atom series of jackets. This makes the jacket a little bit warmer overall. The octa insulation breathes better than the CoreLoft insulation used in the Atom series too. Making it warmer, yet more breathable.
The elastic cuffs feel much more robust than the Atom SL cuffs. They’re also more comfortable pulled up your forearm. The arms are also a little longer and make it more suitable for climbing. The shoulders also have a little more room in them, giving you great freedom of movement when you have your hands overhead.
The two chest pockets are great placement. They’re placed high so you can access them easily with a harness or backpack on. The pockets are also big enough to fit a large cell phone with a rugged case. I often have my phone in one pocket and a map in the other.
The athletic fit is really comfortable. When backpacking or camping I wear the jacket all evening under my down jacket and I usually sleep with both my down jacket and the proton FL on.
Versatility for All Kinds of Mountain Activities
The Proton FL is categorized as a rock climbing and alpinism layering piece on Arc’teryx website. However, I think that classification is underselling its’ versatility in a much wider array of dynamic use. This would be my first choice jacket for all things mountain. Trail running, hiking, scrambling, climbing, ski touring, and backpacking.
The benefit of the hydrophobic octa insulation is that it can be totally soaked yet still retain its’ warmth. If the jacket does get totally soaked, you can wear it while it’s drying during your activity. It will completely dry while being worn within two hours. When you’re in the backcountry and weather takes a turn for the worse, this is the jacket you want to rely on for warmth.
I mentioned I still often pair the Proton FL with a down jacket. Down is still the warmest fibre available per its’ weight. Down’s performance in active pursuits is easily compromised however. I pair the two jackets together because the Proton FL is my “do it all” active layering piece. My down jacket is my “keep me as warm as possible” at camp piece.
Crossing Iceland in the Proton FL
Because of the nature of our expedition, we didn’t pack anything that wasn’t absolutely crucial. No luxury items and only equipment that we had already stress tested and could fully rely on to keep us safe and dry.
Iceland’s weather is absolutely crazy. This is coming from a Canadian. It can go from 20 degrees and sunny and within minutes of a wet fog rolling in, it can drop to nearly freezing. The cool thing about the Proton FL, I never needed to take the layer off. In 14 days of trekking, I almost never overheated, and I was never hiking cold.
I really believe that if we were wearing a lesser jacket and had to layer up and down more often, the trek would have taken longer to complete. Knowing the kind of pain we were in from walking nearly 50km a day with a heavy pack, the effort of stopping to take layers on and off, adjusting our pack multiple times a day, it would have been a time and moral killer.