Arcteryx Mens Proton LT Hoody Neptune


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Other colours available:
Arcteryx Mens Proton LT Hoody Iliad
Arcteryx Mens Proton LT Hoody Labyrinth
Arcteryx Mens Proton LT Hoody Neptune
Arcteryx Mens Proton LT Hoody Sambal

The Proton LT is a synthetically insulated jacket designed with breathability in mind. The air-permeable outer fabric makes it perfect for use as a midlayer in super cold conditions, or an outer layer when moving quickly. 


Climbing equipment designed for efficient movement and protection in alpine environments.


Air permeable mid layer insulation with abrasion and weather resistant outer surface.


High performance, minimalist design that is durable for its weight.

Arcteryx Mens Proton LT Hoody Neptune

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What is the Proton LT?

If you're familar with Arc'teryx's hugely popular Atom LT, you'll recognise where the Proton gets its good looks from. Don't get them confused though, these are two very different beasts! The Proton is designed with exceptional breathability in mind, whether that's as a midlayer in super cold conditions, or as an outer layer when moving quickly.

What is it made of?

Insulation: Providing the warmth inside the Proton is an air-permeable (wind passes through) Coreloft Compact 80 insulation. This synthetic insulation will still provide warmth when wet, will compress down to a fraction of its original size and is nice and easy to take care of. Coreloft Compact 60 is used in the hood to minimise weight and pack size where you require less warmth.

Outer fabric: The primary feature of the Proton is its outer fabric. Unlike the majority of insulated jackets which will feature a wind-resistant outer fabric, the Proton's is air-permeable, meaning air can pass through. This means that the insulation traps your warmth, but air can pass through to cool you down when you're working hard. Think of it like a tent; you open the vents to allow air to pass through to provide a comfortable micro-climate, much like the inside of your jacket. Despite its exceptional breathability, it will repel water and is tough enough to put up with the abuse that climbing and mountaineering have to offer. 

What are the features?

Starting at the top, you get a helmet compatible insulated hood, one chest pocket, two insulating hand pockets, a No Slip Zip (the zip won't slip, if you hadn't already guessed) and lastly dual hem adjustments to seal in warmth. 

How does it fit?

Much like an Atom LT! If you haven't tried an Atom, the Proton fits into Arc'teryx's 'trim' fit block and is a regular/slight short length, features plenty of room in the shoulders and feels brilliant when on. For reference, the centre back length is 75cm.

Where does it fit in the layering system?

The Proton, due to its fantastic breathability, can either be used as a warm midlayer with a shell over the top or an outer layer when moving quickly. 

  • Exceptionally breathable
  • Water resistant
  • Air-permeable
  • Two hand pockets
  • One chest pocket
  • Insulated hood
  • Dual hem adjustment
Code : 24007-NEP-

Season : 2020S R

Weight : 0KG

Sizing Information

Arc'teryx Men's Jackets & Shirts Sizing Information

Measurements refer to body size, not garment dimensions.

  Chest Waist Hip Sleeve
X-Small 36" 29" 36" 32"
Small 38" 31" 38" 33"
Medium 40" 33" 40" 34"
Large 43" 36" 43" 35"
X-Large 46" 39" 46" 36"
XX-Large 50" 43" 50" 37"
  Chest Waist Hip Sleeve
X-Small 92cm 74cm 92cm 81cm
Small 97cm 79cm 97cm 84cm
Medium 102cm 84cm 102cm 86cm
Large 110cm 94cm 110cm 89cm
X-Large 118cm 99cm 118cm 91cm
XX-Large 128cm 110cm 128cm 94cm

Next to Skin Fit: Cut snug to the body through the entire garment to enhance moisture management and thermal efficiency.

Slim Fit: Cut slim to the body through chest, waist, hip and thigh for a low profile fit.

Regular Fit: Cut comfortably from the body through bust/chest, waist, hip and thigh for a classic fit.

Relaxed Fit: Cut loosely through the waist, hip, and thigh for a casual fit.


Measure around your chest/bust, holding the measuring tape under your armpit.


Measure around your waist at the narrowest part.


From a standing position, measure from your crotch to your ankle.


With your arms in a slightly bent position, measure from the centre of the back of your neck, along the length of your arm, to the wrist.


Measure around your hips at the widest part.

Technical Information

Weight: 400g


- Fortius Air 20 (84% nylon, 16% elastane)

- Dope Permeair 20 (100% nylon)

- Coreloft Compact 80 (100% polyester)

- Coreloft Compact 60 (100% polyester)

Care & Advice

How Should Your Insulated Jacket Fit?

Insulated jackets are pedantic little things. Too tight and you'll compress the insulation and limit the warmth capabilities of your brand new jacket, too loose and you'll spend hours warming up the dead space inside the jacket. Getting the correct fit isn't just about aesthetics, it will determine how warm you are. 

The Incorrect Fit

Too loose: A jacket which is too loose will keep you relatively warm, however it will take far longer to do so and will waste large amounts of your precious energy. An insulated jacket works by trapping the natural heat that your body gives off in the fibres of the insulation; this creates a micro-climate inside your jacket, keeping you warm and toasty. If your jacket is too loose, heat will be able to escape through the hem, the sleeves and the neck of the jacket; it's a little like sticking the heating on in your car with the windows cracked open - it will heat up, just incredibly slowly.   

Too tight: A jacket which is too tight is arguably worse than one that is too loose. If your jacket is far too tight, the baffles can compress to a point where the insulation can't loft effectively, limiting the amount of warmth it can trap. Essentially, it won't work! 

The Correct Fit
It's a tricky one to explain, but it's somewhere in the middle. You've first got to consider how many layers you'll tend to wear underneath; will you have just a t-shirt then the jacket, or possibly a baselayer, midlayer and then the jacket? When you've figured out your layers and you've popped your insulated jacket over the top, you shouldn't have any dead space inside. The cuffs and hem should be comfortably sealed around your waist and wrists with room to move. You should be able to lift an arm up above your head without the hem of the jacket lifting more than an inch or so, and the sleeves should be long enough that when carrying out the same motion, they aren't mid-way up your forearm. Your shoulders and chest area should have enough room so that your hands can touch behind your back without feeling restricted. 

Additional Information
Lastly, consider which activites you'll primarily be carrying out while wearing the jacket. Are you primarily using it as a winter climbing piece, or an everyday/dog walking jacket? You'll find that technical climbing jackets tend to feature a shorter cut, while urban and casual jackets feature a longer cut to offer additional warmth with less mobility.

To see examples of what a badly fitting and correctly fitting jacket looks like, click here.

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Arcteryx Mens Proton LT Hoody Neptune

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Excellent customer service. Really detailed easy to understand product descriptions on the Trekitt website, and gear reviews on the Trekitt YouTube channel made it so easy to choose the right backpack for me.

Emily - May 2020

Amazing service! Very helpful in regards sizing and what most matched my needs, despite this being done over the internet. YouTube videos of products being examined are very useful also. Would definitely use again, very fast and efficient delivery. Brilliant! Highly recommended!

David R - April 2020

Highly recommend. I usually go to the shop in Hereford as staff are alwasy very helpful and knowledgeable. So this was the first time I have purchased online and the service was just as good as the shop.

Grizzy - April 2020

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