Bonfus Framus 58 vs Bonfus Aerus 55L
Quick take: The Bonfus Framus 58 costs $20 less; the Bonfus Framus 58 carries more (58 vs 55 liters).
Which one to buy
Ultra 200X with taped seams and 1.75 lbs on the scale, from one small European maker: the bags are nearly twins. What $20 more buys in the Aerus 55L is airflow: a tensioned mesh panel suspended off a curved aluminum frame with carbon cross elements, the trampoline back usually found on much heavier packs. The Framus 58 uses a contact back, two removable shaped aluminum stays over EVA foam, and is rated for a higher load, 40 lbs against the Aerus's 33.
That difference in carry is the real decider. A trampoline back keeps a sweaty shirt off the pack in hot weather, but it pushes the load away from your spine and can feel less stable. The Framus keeps weight close, and its 58 L and stays make it one of the few packs this light that handles a bear canister plus a long food carry. Its stays also come out to strip it down for light trips.
Fit information favors the Aerus. It publishes torso limits for S, M and L and offers two hipbelt lengths, though hipbelt pockets cost extra. The Framus comes in S, M and L with no adjustment, so measure carefully against Bonfus's chart, since exchanges from a small European maker mean international shipping. The Framus's laminate is abrasion-sensitive at the folds and hard to field-repair, which applies equally to the Aerus's fabric. The Aerus pays for its cooler back with some stability and seven pounds of rated load.
Bonfus Framus 58
For thru-hikers who need canister room and a long food carry, and want the load riding close on a contact back.
Bonfus Aerus 55L
Worth the extra $20 for hot-weather hikers who keep loads under 33 lbs and want a ventilated back without leaving the sub-2 lb class.
| Spec | Bonfus Framus 58 | Bonfus Aerus 55L |
|---|---|---|
| Price | $369 | $389 |
| Rating | — | — |
| Type | Ultralight Pack | Ultralight Pack |
| Frame Type | Internal Frame | Internal Frame |
| Capacity | 58 L | 55 L |
| Weight | 1.75 lbs | 1.75 lbs |
| Max Load | 40 lbs | 33 lbs (15 kg) |
| Torso Fit | Sized S / M / L | Sized S to 18 in / M to 19.5 in / L to 22 in; hipbelt short 29.5-39 in or M/L 33-43 in |
| Material | Challenge Ultra 200X | Ultra 200X with taped seams (UltraGrid option) |
| Back Panel | 2 removable shaped aluminium stays with EVA foam | Tensioned mesh suspended off a curved 7075 aluminium frame with four carbon-fibre cross elements |
| Adjustable torso | No | No |
| Ventilated back | No | Yes |
| Raincover included | No | No |
| Hipbelt pockets | No | No |
| Removable lid | No | No |
| Hydration sleeve | No | No |
| Fits BV500 bear can | No | No |
| Warranty | Bonfus warranty: 2 years from receipt against material defects and workmanship failure; original owner, excludes normal wear and tear | Bonfus warranty: 2 years from receipt against material defects and workmanship failure; original owner, excludes normal wear and tear |
Pros & cons
Bonfus Framus 58
- ✓28 oz for a framed 58 L pack is an outstanding ratio, beating the Kakwa 55 and Mariposa 60.
- ✓Challenge Ultra 200X is a UHMWPE and polyester weave laminated to a waterproof film rather than a coated fabric, so it does not wet out.
- ✓Two shaped aluminium stays are removable, so the pack can be stripped further for light trips.
- ✓58 L handles a bear canister and a long food carry, unlike the 37-40 L frameless options.
- ✓EVA foam backing adds comfort without much weight.
- ✓Taped seams throughout, which is rare even in this segment.
- ✓Undercuts the Zpacks Arc Haul Ultra by $30 at nearly the same volume.
- ✗$369 is expensive, and Bonfus is a small European operation with limited US support.
- ✗Ultra 200X is abrasion-sensitive at the folds despite its tear strength.
- ✗Hipbelt pockets are sold separately.
- ✗Lead times can be long and stock is intermittent.
- ✗The laminate is difficult to field-repair compared with a woven nylon.
- ✗No adjustable torso; sizing must be chosen correctly at purchase.
- ✗Limited retail presence means trying one on before buying is unlikely.
Bonfus Aerus 55L
- ✓One of very few ultralight packs with a true suspended-mesh ventilated back.
- ✓795 g in the medium is light for a framed 55 L with that suspension.
- ✓Ultra 200X body with taped seams sheds water well.
- ✓Three torso sizes and two hipbelt lengths.
- ✓Bonfus publishes a clear 33 lb load rating.
- ✗$389 is among the highest prices for a 55 L ultralight pack.
- ✗Hipbelt pockets are a $27-each extra.
- ✗33 lb is a lower ceiling than some framed 55 L rivals that carry 35-40 lb.
- ✗A trampoline back pushes the load away from the spine, which can feel less stable than a contact back.
- ✗No stated hydration sleeve or bear-canister fit.
Bonfus Framus 58 vs Bonfus Aerus 55L: common questions
Which Bonfus carries a bear canister better?▾
The Framus's 58 L and two shaped stays make it one of the few packs at this weight that handles a canister plus a long food carry. Bonfus doesn't describe bear-canister fit for the Aerus 55L, which holds 47 L inside plus 8 L in external pockets.
How do I choose a size without trying one on?▾
The Aerus publishes its limits: S to 18 in, M to 19.5 in, L to 22 in, with hipbelts at 29.5-39 or 33-43 in. For the Framus, measure carefully against Bonfus's chart, because there's no adjustment afterward and exchanges involve international shipping.
Is the trampoline back on the Aerus worth it?▾
In hot weather it keeps air moving across your back. The trade-off is that it holds the load farther from your spine, which can feel less stable than the Framus's contact back, and the Aerus is rated to 33 lbs.