Sierra Designs Flex Trail 40-60 Backpack

The Sierra Designs Flex Trail 40-60 Backpack is ultralight and expandable, with an adjustable torso length, top zippered access, and a great price tag.

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Key features & benefits

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What is in the name

Expandable design

The most important are the numbers 40-60 in the official name of the pack. The meaning is that you can expand the pack, so you can have any volume in the range 40-60 liters. They have added two baffles on the sides of the pack that allow for such an expansion.

There are no many backpacks on the market with such a feature. The best known are those from Deuter, many of them are presented here in the site. That brand makes packs with an expandable collar, so the pack’s length may change dependent on the stuff you carry.

However, in this Sierra Design’s pack you have four pairs of straps that allow for width-wise expansion of the pack. The picture above shows how the pack looks when expanded. In my view, this is a better design than in the Deuter’s packs.

So, if you use a pack with a bulky equipment, like for cold weather tour, you will release those straps and have more volume. Similarly, in a warm environment you might carry less bulky equipment, and then simply cinch the pack and make it smaller.

Yet another situation where this expandable feature plays a role is if you are on a long tour and you start with lots of food and water in the pack. So you expand it in the beginning, and as the items reduce in time, you simply gradually reduce the volume.

Other than that, this is a top loading pack, but with a zippered access. This is the only access to the main compartment and I find it a bit too small. There is no bottom compartment here.

The pack is hydration compatible, with an internal sleeve for a water reservoir, the picture above shows how it looks. The hose port is behind your neck. Below you see the top zipper and a few more details in this part of the pack.

Suspension system

This is an internal frame pack with an aluminum alloy wire that gives it support and shape. You have an adjustable torso length, and the system is a ladder type, you can see it partly below. The sternum strap is adjustable and it is a sliding type.

The hip belt and lumbar area are with a thick foam padding. As for the shoulder harness, I would say the padding is just enough. You also have the usual load lifters in place, they are visible in the pictures.

Pockets

This pack has a standard set of 6 pockets that include the following:

• Two oversized zippered hip belt pockets, one shown below.

• Two large stretch mesh side pockets, see the side view picture above. They can easily accommodate 1.5 liters bottles.
• One large stretch mesh pocket is on the front.
• One smaller zippered pocket is on the front-top area of the pack.

There is also one inner zippered pockets for valuables.

Compression straps and loops

You have already seen the most important straps used for expansion. The pack also comes with a pair of webbing loops on the bottom where you can attach an ice axe and trekking poles. Use one of the compression straps above together with these loops. 

Fabric

The main fabric is 150D ripstop polyester, so it is quite thin. In more exposed areas you have a much more durable 420D fabric.     

Please see more in this short video:

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Who is it for

Regarding the best use & capacity, clearly, you have at least two packs here in one. When compressed, it is small enough even for day tours.

But you can expand it and have 50% more volume, and this is indeed remarkable. In this state you can use it for longer tours.

You have already seen its adjustable torso length, so this pack can be used by different family members and each of them will be able to find a perfect fit. 

Regarding the weight, the pack is in the groups of ultralight items of this type. It weighs only 2 lb 12 oz (1.23 kg), so its volume-to-weight ratio is simply excellent 45.5 liters/kg. 

To realize how good this is, compare it with other exceptionally light packs like Kelty Outskirt 50 Backpack where this ratio is 38 liters/kg, and the Osprey Exos 58 which weighs 2 lb 13 oz (1.28 kg) and its volume-to-weight ratio is 45 liters/kg.

Regarding the price, it is simply excellent, you can check for updates in the links below.

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Specifications

• Weight: 2 lb 12 oz (1.23 kg).
• Carry weight: 45 lb (20 kg).
• Volume: 2380-3417 in³ (39-56 L). 
• Dimensions (H x W x D): 27.5 x 10.5 x 14 in (70 x 27 x 35 cm).
• Torso fit: 15.5-21 in (39-53 cm).
• Hip belt fit: 31-54 in (79-137 cm).

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Final thoughts & rating

Below you can see how I rate this pack against my usual rating criteria so that you can easily compare it with other items of this type:

 

BEST PLACEs TO BUY

Sierra Designs

For more options, please check under the category Large Packs.

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