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Quality oozes from every stitch and seam of the Bonfus Framus 58L. This pack is meant to be carried for weeks at a time and come out of this all unscathed. Since it's designed for weeks on the trail, it carries weight much better than other ultralight packs we tested. Weighing just 26.6 oz, with an internal volume of 55 L and a stated load limit of 40 lbs, the Bonus Framus is ready for some seriously long carries. These stats should raise some eyebrows from experienced ultralight hikers looking to tackle a long trail like the AT, PCT, or CDT.
REASONS TO BUY
Impressive quality
Distributes weight well
Comfortably carries 40 lbs
REASONS TO AVOID
Lacks hip-belt or shoulder-strap pockets (optional)
Finicky roll-top design
Non-removable hip belt
Updated Version Available for 2026
The Framus 58L that we tested was purchased in 2025. The pack has been updated since then, with revisions to the hipbelt, larger side pockets, and a stretchier, more durable material for the front pocket. The side elastic cords are fully removable, and there are 16 new external attachment points that can be paired with Bonfus's 15 mm Gatekeeper straps (sold separately) to lash bulky items to the outside of the pack.
This high-capacity ultralight pack is specially designed to carry heavy weight over many miles, though it lacks some common features
This pack wowed us with its perfect set of features, comfortable design, and impressively large carrying capacity
A tough, voluminous, and reasonably priced ultralight backpack that's perfectly designed for long trips
An excellent pack for those who want to move up from a conventional backpack, but don't want to lose out on creature comforts
When it comes to frameless ultralight packs, this one leads the way in weight, design, and innovation
Rating Categories
Bonfus Framus 58L
Gossamer Gear Maripo...
Durston Kakwa 55
Osprey Exos Pro 55
Nashville Pack The C...
Comfort(40%)
8.0
10.0
8.5
9.0
7.5
Ease of Use(25%)
7.0
8.0
9.0
9.0
6.0
Weight-to-Volume Ratio(20%)
9.1
7.2
9.3
6.6
10.0
Adjustability(15%)
6.0
8.0
6.5
7.0
10.0
Specifications
Bonfus Framus 58L
Gossamer Gear Maripo...
Durston Kakwa 55
Osprey Exos Pro 55
Nashville Pack The C...
Measured Weight
26.6 oz
34.3 oz
31.0 oz
33.2 oz
22.0 oz
Stripped Weight
21.3 oz
18.0 oz
27.5 oz
30.4 oz
17.3 oz
Advertised Volume
58 L
60 L
70 L
55 L
40 L
Measured Volume (Main Compartment)
54 L
54 L
55 L
46 L
43 L
Weight per Liter (Full Pack)
0.46 oz/L
0.57 oz/L
0.44 oz/L
0.60 oz/L
0.40 oz/L
Sizes Available
Torso: Short, Medium, Large
Torso: S, M, L
Hip Belt: S/M Curved (w/ S torso), M Straight (w/ M and L torso); other hip belts sold separately
Torso: S, M, L
Hip Belt S/M, M/L
Torso: S/M, L/XL
Torso: 16', 18", 20"
Hip Belt: S (28"-38"), M (32"-42"), L (26"-48")
Should Straps: 16", 17.5", 19", 20.5"
Organization Compartments
Side pockets, center pocket, main compartment
Top flat zippered pocket, three total side pockets, center pocket, dual zippered pockets on hip belt, main compartment
Side pockets, side zipper pocket, center pocket, hip belt pockets, strap pockets, main compartment
Lid, mesh side pockets, center pocket, dual zippered pockets on hip belt, main compartment
Main compartment, center pocket, running vest-style pockets, back-entry bottom stash pocket
Hydration Compatible
No
Yes
No
Yes
No
Side Pocket 700ml Smartwater Capacity
2
3
3
5
Continuous wraparound pocket
Single Hip Belt Pocket Capacity
N/A
6 Clif Bars
10 Cliff Bars
4 Clif Bars
N/A
Removable Frame and Hip Belt
No
Yes
No
No
Yes
Sternum Strap Whistle
No
Yes
No
Yes
No
BearVault BV500 Compatibility
Excellent
Good
Excellent
Good
OK
Frame Type
2 removable shaped aluminum stays and removable EVA foam back padding
Removable SitLight foam pad / removable stay
Removable foam pad / removable stay
3.5 mm powder-coated LightWire frame
None
Fabric
Challenge Ultra 200X
100D & 210D recycled Robic nylon
Challenge Ultra 200x
NanoFly: 100D nylon x 200D UHMWPE ripstop
210D Venom Gridstop ECO
Our Analysis and Test Results
Challenge Ultra 200x and 400x fabric on the pack body, and 210d UltraGrid on the straps, hip belt, and side pockets keep the Bonfus Framus light, yet durable enough to trust on a multi-week trip. Internal frame stays, load lifters, and a beefy hip belt help distribute heavier loads to your hips, helping save your shoulders. Our only wish is that some of the accessories, like hip belt pockets and a shoulder strap pocket, came standard.
The Bonfus Framus is an excellent high-capacity backpack, with 54 L of internal capacity and a 40 lb load limit. Credit: Justin Simoni
Likes
For a total weight of just 26.6 oz, we measured the internal volume of the Bonus Framus at around 54 L, close to the manufacturer's claim of 55 L. With all of this capacity, this pack has a very impressive weight-to-volume ratio of 0.46 oz/L.
This internal volume is supplemented by a stretchy mesh center pocket that swallowed five 1-liter Smartwater bottles, and two side pockets with stretchy openings that held two 1L Smartwater bottles each.
We measured the internal capacity at approximately 54 liters. Credit: Justin Simoni
The Framus is sewn using the very durable, tear- and water-resistant Challenge Ultra 200X pack fabric. The bottom of the pack uses Challenge Ultra 400x – a heavier, burlier variant of 200x for increased abrasion resistance.
The bottom of the pack features much heavier Ultra400 material for enhanced durability. Credit: Justin Simoni
Seams are heavily taped for water resistance, but the manufacturer still recommends using a pack liner. Credit: Justin Simoni
The Bonus Framus comfortably carries weight better than many other packs we tested. The manufacturer suggests a maximum load limit of 40 lbs, which felt very reasonable.
Removable internal metal stays and internal foam padding add back support. Load lifters and a fairly burly hip belt with moderate lumbar support evenly distribute weight across your entire back.
Well designed load lifters help adjust how the load carries on your back. Credit: Justin Simoni
Removable metal stays help transfer weight to the hip belt (and off your shoulders) while also allowing the load lifters to work effectively. Credit: Justin Simoni
Dislikes
As much as we love this pack in general, we missed having pockets on the hip belts for snack storage and easy access on the go. Accessories like this one, as well as shoulder-strap pockets, are offered by the manufacturer, while other companies provide these as standard features of the pack.
The hip belt is easy to adjust, but lacks pockets which would give you more storage options. Credit: Justin Simoni
This pack is a bona fide ultralight pack, so if you are looking for creature comforts, you won't find many. We give the Bonus Framus kudos for its removable back padding and frame stays, which help shed a bit of weight. However, the hip belt isn't removable, which is a common feature among other packs so that they can also be used as a day pack.
Adjustability is also slightly hampered by the roll-top design. The snaps help keep the top of the pack closed while you roll it up, but instead of snapping together over the top, the top buckles clip into straps down the side. It's nice that you can adjust the pack's height or cinch it down between resupplies, but it's harder to close when it's fully loaded.
The top of the Framus opens up wide to swallow gear, but tapers dramatically toward the bottom. Credit: Justin Simoni
The top snaps are a nice touch to keep things in place while you roll down the pack, but we wish the two sides buckled together rather than onto separate side straps. Credit: Justin Simoni
Should You Buy the Bonfus Framus?
The Bonus Framus will likely appeal to ultralight hikers willing to sacrifice some creature comforts for additional back support. This pack is a solid choice for taking on some serious miles. However, it fits in a bit of a niche between lighter-weight and more minimalist ultralight backpacks.
What Other Ultralight Backpacks Should You Consider?
The Durston Kakwa 55 is a very similar option, though it comes with both shoulder-strap and hip-belt pockets and is even cheaper than the Bonus Framus. The exterior back padding on the Ultralight Adventure Equipment Ultra Circuit helps with perspiration, which can be a bit of a problem if you're carrying a heavy load with the Bonus Framus. Unlike these larger-capacity packs, the Hyperlite Mountain Gear Unbound 40 is our favorite for thru-hikes, thanks to unique features that enhance gear storage and accessibility.
