Choosing a rucksack is not as easy as you'd think. With the help of international explorer Mikael Strandberg we reviewed the Berghaus Bioflex 45 and found that it's a specialist sack, but not for everyone.
Fantastically light and featuring an intriguing support system, we took an immediate liking to this rucksack.
But how would it fare once put to the test, and is it the right sack for your back?
On an expedition a 45-litre rucksack is one you take with you to use as a daysack - there's simply not enough room for enough gear to last longer.
I'd take it with me if mid-expedition I wanted to climb a peak, or take a longer detour and needed spares and supplies, but you'd struggle to get a sleeping back, roll matt and decent tent in a rucksack of this size.
The Bioflex System
Bioflex is a system that's designed to twist and move as you do - unlike most rucksacks that stay fixed. I like it as it allows you to move more freely. It does look and feel a little odd to start with, but with 15kg loaded it felt comfortable enough.
That said, it's not a rucksack for huge loads and should be chosen to match what you'll use it for. Alpinists will like it better than explorers. There's too many straps for my liking and under heavier loads the top straps start to cut in.
I'd load no more than 10-12kgs and with this it will be fine.
Berghaus has clearly worked hard to cut weight, and while this is welcome, it restricts the practical uses of such a smart rucksack.
Friends have said similar things about the Bioflex system.
Johan Ivarsson, an old expedition partner of mine, said that with 35kg loaded and they found the same issues when the rucksacks had to take the strain and found failings with the Bioflex set up in earlier models.
The rucksack tested here has the second-generation system and a frame that's 70% lighter. Also worth noting that in the smaller size you don't get a height adjustable back.
It does feature a clever zip entry for stashing your wet gear without it spoiling other contents, and handy external mesh pockets and zippered stash points.
Pick your task, pick your rucksack
So it's very much a rucksack for a specific task, or one to not be overloaded. My wife and I found them comfortable over a few days, which will be plenty enough for most people.
However, we are all different and you should choose rucksacks carefully and take your time before you part with your cash.
Berghaus makes possibly my favourite rucksack, the Berghaus Vulcan, and when you compare the two it's clear that they both suit very different roles, which is exactly why you need to know first what it is you want, before you consider buying the Bioflex 45.
I'd definitely rate the rucksack as expedition worthy, but with a limited role.
More about the Berghaus Bioflex 45
About Mikael Strandberg: Mikael is a Fellow of the Royal Geographical Society, the Explorers' Club, Travellers Club and the Long Riders Guild and considered by the Explorers' Club to be "the best contemporary explorer in the world" at the present.