Gossamer Gear G4-20 Ultralight 42 Review

Overview

The Gossamer Gear G4-20 is a 42-liter frameless backpack suited to a wide range of trips, from ultralight thru-hiking and hut-to-hut trekking to all-day peakbagging and fast-and-light overnights.

In many ways, it repackages many of the unique features of Gossamer Gear’s Mariposa 60 into a lower-volume, lighter-weight form

— a genuine do-it-all pack for the sub-10 lb base-weight crowd. At $205 and under 26 oz in any size, it’s one of the most feature-complete ultralight frameless packs available without demanding a boutique price tag.

Key Specs

Spec	Detail
Total Volume	42L (30L main + 12L pockets)
Weight (S/M/L)	658g / 709g / 740g
Material	70D & 100D Recycled Robic Nylon, DWR, PFAS-free
Frame	Frameless (removable molded sitpad)
Max Load	30 lbs (20–25 lbs recommended)
External Pockets	6
Sizes	Small, Medium, Large
Price	~$205
Comparison	See how G4-20 compares to similar gear

Performance

Load Carrying

This is where you need to calibrate your expectations up front. Gossamer Gear lists the G4’s max load at 30 pounds, but 20–25 pounds is a more realistic range. While the foam pad helps it hold its shape and the hip belt is sewn onto the pack, the G4 is still a frameless backpack that doesn’t transfer much weight to the hips — the hip belt is wide and richly padded, but it isn’t firm enough for significant weight transfer. That’s not a knock on the pack specifically; it’s just the physics of going frameless. In testing, the pack is comfortable with a standard ultralight/thru-hiking base weight and three days’ worth of food. The hip belt is large and well padded, which matters on a frameless design. Push past 20 lbs and you’ll start to feel it, especially on uneven terrain. One recurring complaint from users is that the pack can sag off the backside and put too much weight on the shoulders, and cinching the hip belt very tight to compensate isn’t always comfortable.

If you’re committed to keeping your loaded weight in the 18–22 lb range, the pack is extremely comfortable at or below 25 lbs, and it’s seen action on demanding routes. One BPL user has taken it on every trip since 2020, including remote routes like the Hayduke Trail and mainstream thru-hikes like the AT and CDT.

Organization & Pocket System

This is where the G4-20 earns genuine praise — and a little controversy. The two side pockets are asymmetrical: one is short and reachable while wearing the pack (ideal for a water bottle), while the taller one is flexible — useful for tent poles and stakes, saving room in the main compartment. Hikers either love this setup or find it awkward; I think it’s clever if your kit happens to fit the mold.

The hip belt has two pockets: one large enough for a phone, closing with a waterproof zipper, while the other is an open mesh pocket good for snacks — and items you don’t mind losing.

That mesh/bungee hip pocket is the most consistent complaint across reviews.

The bungee retention is strong, but on occasion a snack bar has popped out during scrambling — it’s not something to trust with anything more than a granola bar.

Two zippered hip belt pockets would be better.

There’s also a zippered pocket above the front stretch pocket — good for odds and ends like tent stakes, toiletries, or extra snacks.

The G4-20 carries weight lower on the body, making the hiker feel more stable and less top-heavy, especially over uneven or steep terrain.

Closure & Compression

The roll-top closure makes it easy to load and unload, and can extend capacity if necessary. The two closure options are to roll the top down and clip the buckles to the two side straps, or to roll the top and clip it together in the center with a single buckle like a dry bag.

The side straps and top cinch strap are easily removable, which is a nice touch — most ultralight backpackers will pull them off, but they’re there if you need to compress a lighter-than-usual load.

Materials & Durability

Made from 70D and 100D Robic Nylon, the G4-20 is moderately durable compared to some competitors, but is plenty durable with proper care.

Gossamer Gear has transitioned to PFAS-free recycled fabrics across all their packs

, which is a meaningful step in the right direction for an outdoor brand.

The DWR coating will help keep gear dry in light rain, but you should opt for a pack liner for maximum protection.

The 70D panels will show wear before something like a Hyperlite DCF shell would, so be mindful with sharp-cornered gear and abrasive surfaces.

Back Panel & Ventilation

Though the molded back support pad has ventilation holes for airflow, it can feel hot and sweaty since it’s non-absorbent — the upside is that it dries quickly after breaks.

If breathability is a priority, GG’s Air Flow SitLight Camp Seat is a drop-in upgrade.

The sitpad itself is worth the weight it adds. It functions as back padding while hiking and a cushy seat when you stop to rest. You can swap it for something else, like the Z Seat from Thermarest, or go without if you prefer to shed a few grams.

Pros & Cons

Pros

• Under 709g (medium) with a genuinely useful sitpad included
• Clever pocket layout — six external pockets covers most on-trail needs
• Roll-top with dual closure options is simpler and more intuitive than GG’s fold-over system

• Compared to some $400 options on the market, the G4-20 delivers exceptional value without sacrificing performance

• Removable compression straps let you strip the pack down or keep options open
• PFAS-free recycled Robic fabric is a meaningful sustainability upgrade
• Three sizes with good torso-range overlap for accurate fit

Cons

• The hip belt is fixed — sewn directly to the back of the pack and not removable or interchangeable like most other GG packs

  , which is a real limitation for hikers who prefer to run beltless
• Open mesh/bungee hip belt pocket is unreliable for anything you’d be upset to lose
• Back panel runs warm; no meaningful ventilation channel

• J-straps only — hikers with more square or broad shoulders may prefer S-straps, which Gossamer Gear does not offer

• Bear canister use is uncomfortable without a rigid frame or framesheet
• The 42L volume figure includes all external pockets — the true main compartment is 30L, which matters if you’re cross-shopping with brands that measure differently

Who Should Buy This

The 42L capacity is about right for a minimalist frameless pack where you’ll need to keep your base weight around 10 lbs.

This is the sweet spot buyer: a three-season thru-hiker or section hiker who’s already invested in a lean kit — shelter under 20 oz, a quilt, a light sleep pad — and wants a pack that works with that system rather than against it.

It isn’t so small that you have to be extremely ultralight to make it work, but it’s small enough that you get to carry a lightweight pack

, which makes it a reasonable entry point for someone moving from a heavier framed setup. It’s not the right call for winter trips, heavy food carries of more than five days, or anyone who regularly encounters bushwhacking terrain that’ll chew through lighter fabrics.

Verdict

The G4-20 is the rare ultralight pack that doesn’t ask you to sacrifice usability for weight savings. The pockets are thoughtfully placed, the roll-top is clean, and the removable sitpad adds genuine multi-use value. The fixed hip belt and mesh-only hip pocket are real trade-offs, and you need to be honest with yourself about your loaded weight — this pack wants to carry 20 lbs, not 28. At $205, it sits well below the Zpacks and HMG alternatives while matching or beating them on everyday trail utility for most hikers. Rating: 8/10.