Bonfus Altus Custom Pack Review

Overview

The Altus is Bonfus’s build-your-own frameless pack — you pick the torso length, fabric, shoulder strap style, and a handful of add-ons, and they sew it to order. At a 38L total volume (30L main body plus 8L of external pocket space) it sits in the sweet spot for warm-weather thru-hiking and fastpacking rather than winter expedition loads, and it’s aimed at people who already know their gear list well enough to spec a pack around it rather than buy off the shelf.

Key Specs

Spec	Detail
Brand	Bonfus
Frame type	Frameless
Total volume	38L
Internal (main body) volume	30L
External pocket volume	8L
Average circumference	85 cm
Unrolled height	73 cm
Starting weight	365 g (excludes hip belt option)
Shoulder strap options	Standard S-curve or Vest-style (+95 g)
Shoulder pocket	1 included, second +12 g
Customization	Torso length, fabric, strap style, pockets

Performance

Because the Altus is made to order, “performance” really splits into two questions: how good is the build, and how good is the fit you end up with.

On build quality, Bonfus leans on the details that matter for durability on a frameless pack. The attachment points of the shoulder straps to the back panel are reinforced with a double layer of UltraGrid fabric, for extra tear resistance, which is exactly where frameless packs tend to fail first once you’re loading them past 10-12 lbs. The straps themselves are 11mm (7/16”) thick and 7cm (2.75”) wide, padded with EVA-foam and 3D spacer mesh, which is on the burlier end for a sub-400g pack — most cottage frameless packs in this weight class use thinner, less padded straps. Bonfus also includes a drainage hole at each side pocket, taped seams, small touches that show up in long-term durability rather than a first impression.

The compression system is worth calling out specifically: the pack uses functional 4-point compression cords that fully cover the pack sides from top to bottom, allowing you to significantly reduce pack volume when needed. On a 38L pack, that matters — you can cinch it down for a 2-day fast-and-light trip and still open it back up for a week of food. The front is a big stretchy spandex/nylon front mesh that stores a lot of gear, which functions as your wet-gear or overflow pocket, standard fare for the category but well executed here.

The strap choice is the biggest performance fork in the road. The standard strap is a gentle S form, padded throughout their whole length and is the same harness used across Bonfus’s other packs. The vest option, on the other hand, is optimized for stability when fastpacking and running, the same vest strap used in the Fastus 23L pack, and adds mesh storage: it’s padded to the shoulders, composed of breathable mesh for freedom of movement, stretch, and breathability, and features 5 mesh pockets to store two soft flasks and snacks. If you’re doing mostly trail running or fastpacking with soft flasks, the vest strap (+95g) is worth the weight penalty — it keeps the load pinned close and gives you drink-on-the-move access the standard straps don’t.

For context, most commercial frameless packs run 200 to 400g and can consist of not much more than a sack with shoulder straps. At 365g starting weight (before hip belt), the Altus sits toward the heavier end of that range, which tracks with the beefier strap padding and reinforcement — this isn’t the lightest frameless pack you can buy, it’s built to be a bit more durable and comfortable than the bare-minimum sack-with-straps designs.

Independent long-term testing data is thin. I found one YouTube reviewer who reported testing the Bonfus Altus 38L for over a year, using it on dayhikes, multi-day trips and long distance hiking — in heat, cold, rain, and snow, which is a reasonable proxy for durability across seasons, though I wasn’t able to pull specific failure points or wear data from that source. Beyond that and a WildStray blog review, there isn’t a deep bench of Reddit r/Ultralight or BackpackingLight threads on this specific model — Bonfus is a small Slovenian cottage brand and the Altus is more niche than something like a Zpacks Arc Haul or LiteAF pack, so take my performance notes as informed by the spec sheet and design details more than a large sample of user reports.

Pros & Cons

Pros

• Genuinely customizable — torso length, fabric, and strap style let you dial in fit rather than sizing up/down between fixed options
• Reinforced strap attachment points and taped seams suggest better-than-average durability for a frameless pack
• Full-length 4-point compression makes the 38L usable for loads well below its max volume
• Vest strap option is a legitimate fastpacking harness, not an afterthought
• Drainage holes and thoughtful small details throughout

Cons

• 365g starting weight (excluding hip belt) is heavier than minimalist frameless competitors in the 200-280g range
• Frameless design caps comfortable loads — not the pick if you’re consistently over 25-30 lbs
• Made-to-order means you need to already know your torso length and preferences; less forgiving for first-time UL pack buyers who want to try before committing
• Very limited independent long-term reviews and forum discussion to cross-check durability claims against
• Custom orders typically mean longer lead times and no easy returns/exchanges compared to stocked packs

Who Should Buy This

The Altus makes the most sense for an experienced ultralight or fastpacking hiker who already has their base weight dialed in, knows their torso measurement, and wants a pack tailored to a specific fabric/strap combination rather than picking from a fixed size run. It’s a poor first UL pack for someone still experimenting with gear list and volume needs, since the whole value proposition is precision fit.

Verdict

The Altus is a well-detailed, genuinely customizable frameless pack from a small maker that clearly sweats the durability details — reinforced attach points, taped seams, a real fastpacking harness option. It’s not the lightest 38L frameless pack on the market, and the made-to-order model means less room for buyer’s remorse than picking up something off a retailer’s shelf. I’d put it at a 7.5/10: excellent for the hiker who knows exactly what they want, a riskier buy for anyone still figuring that out.