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Gorgeous, super lightweight and incredibly water resistant, the Alpha FL 45 is about as good as it gets for climbing and ascent packs. Recommended for Rock, Ice and alpine climbing.
Gorgeous, super lightweight and incredibly water resistant, the Alpha FL 45 is about as good as it gets for climbing and ascent packs. Recommended for Rock, Ice and alpine climbing.

Arcteryx Alpha FL 45 Backpack Black

£96.00  £160.00  40% off
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Estimated Delivery & Collection Dates

Estimated Delivery & Collection Dates are given on Pre-Order and Pre-Launch products. They are for indication purposes only and can change at any time without notice.

The dates we provide are based on indications given by our suppliers. Whenever we get updated information from our suppliers we will endeavour to update the Estimated Delivery & Collection Dates provided on product pages.

We estimate this will be ready for despatch to you or collection via Click & Collect on the Undetermined

Arcteryx Alpha FL 45 Backpack Black Information

Season : ZZZ Discontinued

Brand : Arcteryx

Code : ARCAFL45B

What is the Alpha FL 45?

Ultralight, weather resistant and about as tough as it gets, the Alpha FL is a stripped-back climbing pack designed for moving fast and light in alpine and general mountain environments. 

What is the backsystem?

There isn't necassarily a backsystem on the Alpha; neither are there any internal stays! Everything stays incredibly stripped-back and minimalist to ensure the highest levels of durability and lightest weight. The load is supported by a laminated HD 80 high density polyethylene foam that also protects your back from protruding contents. The shoulder straps use a laminated construction of burly double weave nylon and soft edged Hypercell foam to distribute the weight without causing hot spots.

What is it made of?

This sublime and utterly gorgeous pack is made using Arcteryx's amazing AC² (Advanced Composite) technology. AC² uses a lamination and coating process to create extremely strong, lightweight and highly water resistant fabrics. This process allows Arcteryx to create an almost seamless construction and allows direct placement of components, such as straps, eliminating stitching. This amazing fabric is then turned into product using complex 3D patterning, heat sealed seams and micro seam taping resulting in strength, stability, structure and minimal weight. The result is a featherweight, extremely water resistant and massively tough climbing and ascent pack. The main body of the pack is made using a high denier ripstop nylon that is exceptionally durable with a high tenacity tear strength and coated on both sides with urethane to create an air-permeable fabric that is 100% waterproof.

What are the features?

The minimal design of the Alpha FL 45 does not include a traditional top pocket closure, instead a canoe bag type closure is used to create an internal watertight seal. An internal roll top secondary collar is bonded to the main pack and seals the contents, this is then protected by a tough nylon ripstop external primary collar with a draw cord closure. These collars can both be extended to provide additional storage. A single lightweight webbing strap clips over the top to secure the load and can be extended to carry ropes. Crampons and ice tools are stored using webbing loops and a simple elastic bungee system that also compresses the load and adds additional external storage. Finally a small external zipped pocket with a key clip finishes off this simply stunning high performance and technically advanced pack.

  • AC² Advanced Composite technology
  • Weatherproof Roll Top  for ultimate protection from rain or snow
  • Extension collar adds additional carrying capacity
  • Glove friendly main opening
  • Revised shoulder and sternum straps for better comfort
  • External bungee compression and carry system, great for crampon bags or belay jackets.
  • Twin ice tools attachment system
  • External WaterTight zipped pocket with key clip
  • Top rope strap anchored on the back panel for easy of use.
  • 4 side lash points that accommodate up to 22mm wide straps

Getting the correct fit for your rucksack is as important as getting the fit right for your boots. A badly fitting pack can inflict misery and discomfort and completely ruin your adventure. This guide is designed to help you get the best fit and comfort from your chosen pack so that carrying all your kit becomes a pleasure and not a chore.


If the pack has an adjustable back length, adjust this to your correct level. Your back length is not related to your height but your torso length. Many packs, and specifically the bigger and more technical packs are available in different back lengths or feature adjustable back systems. Contrary to popular belief, your torso length and not your overall height is the key to getting a well fitted pack. Tall people don’t necessarily have long torsos, just as shorter people don’t always have a short torso length.

Your torso length can be found by measuring from your C7 vertebra (the bony protrusion at the back of your neck when looking down) to the height of your iliac crest (top of your hip bones, where you put your hands on your hips). This measurement will give you an idea of which pack back length to choose.

Once you've got the back length sorted, either by selecting the correct size pack or adjusting the back system, you can begin to follow these simple steps to help achieve a comfortable carry.


Before you start fitting the pack, loosen off all the straps as this will make it easier to get the correct tension later.


Fasten the backpack hipbelt, the general position is the same as where you’d put your ‘hands on hips’ This area is called the pelvic girdle, and what you can feel when you rest your hand on the area is the bony protuberance, the iliac crest. The iliac crest can support the weight from a pack comfortably, and for sustained periods. The padded section of the hipbelt should encompass this and fit securely.

Tighten the straps so the hipbelt feels secure and held firmly around your body. Ensure that the lumbar pad is centered to your lower back to give you maximum support. Remember that your hips carry most of the weight of the pack, so this should be firm but comfortable.


Next, adjust the shoulder straps, pull them until they start to become snug, but ensure that they are not too tight as to lift the pack off your hips. Remember tightening them will stabilise the pack but will increase pressure over the shoulders. If the back length of the pack is correct the shoulder straps will be flush to your shoulders whilst the hipbelt sits in place comfortably. The point where the shoulder straps attach to the main body of the pack should be roughly half way down your shoulder blades; this ensures  that the shoulder straps rolls evenly over the top of your shoulders to distribute the weight correctly.


Fasten the chest strap and pull until taut but not tight, the elastic section should not be extended. This helps keep the shoulder straps from catching in your shoulder joints and keeps the stability of the pack when moving over rough ground.


Top tensioner straps link the shoulder straps to the top of the pack. When tightened, their main function is to stabilise the top part of the pack. The optimum angle for these straps in 45º, but they will stabilise the load even when horizontal or at a more obtuse angle. Tighten them until you feel the top part of the pack rest against your pack, over tightening them will create excessive pressure on the front of your shoulders.


Side tension straps are linked to the hipbelt. By tightening these straps you can stabilise the load but reduce the hipbelt flexibility. Where balance is critical tightening them can help you feel more secure. However, if you are striding out over easy terrain it’s better to loosen these straps to allow full hip flexibility.


Side compression straps come next, pulling these tight does two things: firstly, it stabilises the load, secondly it can lift the lower part of the pack, repositioning the load closer to your back.


Following these steps should give you a comfortable but secure fit on your pack. Sometimes adjustments will need to be made on the go depending on the terrain or the load you are carrying. The perfect fit is very much a personal preference so experiment with different tensions on the pack to find what suits you best.

Technical Information

Weight: 675g

Volume:32 litres - extends to 45 litres


N400r-AC² nylon 6 ripstop

N100mr-HT nylon 6.6 mini-ripstop (primary collar)

N70r-HT nylon 6.6 ripstop (extension collar)

HD-80 Foam

Burly Double-Weave

Hypercell Foam

Sizing Information

Arc'teryx Men's Bag Sizing Information

Sizing refers to your back measurements, not the size of the product.

  Bag Size
Your Back Measurement Short Short-Regular Regular Regular-Tall Tall
  Bag Size
Your Back Measurement Short Short-Regular Regular Regular-Tall Tall
35.5 cm          
38 cm          
40.5 cm          
43 cm          
45.7 cm          
48 cm          
51 cm          
53 cm          
55.5 cm          
58.5 cm          

Measure along the spine between the 7th cervical vertebra and the level of the hip iliac crest


Compare this measurement to the Sizing Charts


It is possible to interchange different size shoulder strap and hipbelt components on many Arc'teryx Packs, but this will not change or affect the back-length of the pack.

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  • Arcteryx Alpha FL 45 Backpack Black Review by B,  On 18/04/2016 07:53:01

    This is a deceptively simple, balanced and well made pack.
  • Arcteryx Alpha FL 45 Backpack Black Review by SzB,  On 01/05/2018 14:24:07

    Exactly what it promised, hard wearing, waterproof, optimal size and comfort, smart, clean design
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