The sub-2-lb framed ultralight pack market has two packs that come up in every serious thru-hiker conversation: the ULA Circuit and the Gossamer Gear Mariposa 60. Both retail between $300 and $315. Both use Robic Nylon construction with framed-but-light architecture. Both show up at PCT and AT trailheads more than anything else in their weight class.
I’ve carried both on extended trail sections with the kind of scrutiny that comes from 12 years of guiding and a healthy distrust of manufacturer claims. The ULA Circuit went through a 57-mile High Sierra PCT section from Vermilion Valley Resort to Reds Meadow in late July 2024 — granite talus, high-alpine passes, afternoon thunderstorms — loaded to 28 lbs with four days of food and 3L of water. The Gossamer Gear Mariposa 60 got a 52-mile shakedown on Vermont’s Long Trail, northbound from the Canadian border to Johnson, in September 2024: classic mud-and-roots Green Mountain terrain, loads between 22 and 30 lbs, and a week of mixed rain and clearing weather.
My test rig: a digital luggage scale accurate to 2g, the Osprey Exos 58 as a carry baseline, and the discipline to run an end-of-trip inspection on every pack — seam integrity under load, zipper function, delamination at stress points, fabric wear at primary abrasion zones.
Both packs are genuinely good. They are not interchangeable. The wrong choice will cost you real comfort at mile 40.
Quick Verdict
Best for sub-30-lb thru-hiking loads: Gossamer Gear Mariposa 60 — OutdoorGearLab’s 2026 top ultralight pick, pivoting hipbelt tracks terrain better, lighter total build
Best for heavy loads and rough terrain: ULA Circuit — 400D Robic Nylon, stiffer multi-component frame, better hipbelt organization for 25–35 lb carries
Best for weekend warriors stepping into UL: ULA Circuit — more forgiving fit range (XS–XXL hipbelt), better pocket access while moving, wider body-type coverage
Best overall value by load range: Mariposa 60 under 25 lbs; Circuit from 25–35 lbs
How I Tested
I weighed both packs myself the moment they arrived — grams on a 2g-accurate digital scale, not manufacturer spec. Load testing used a consistent 28 lb base across both packs: four days of food at 1.5 lbs/day, 3L water, a typical thru-hiker shelter and sleep system. The Exos 58 served as a consistent reference throughout. Each pack got an end-of-trip inspection covering seam integrity under sustained load, zipper function after wet days, and fabric wear at primary abrasion zones. Vermont’s September weather provided continuous rain across two days — more than sufficient to judge each pack’s moisture management without lab simulations.
Pricing Head-to-Head
| Pack | MSRP | Available At | Notes |
|---|---|---|---|
| ULA Circuit (Robic) | $300 | ula-equipment.com only | +$50–$70 for custom color or fabric |
| ULA Ultra Circuit | Not confirmed publicly | ula-equipment.com only | Higher than Robic; exact price not listed on site |
| ULA Circuit SV (48L) | ~$300 estimated | ula-equipment.com only | Launched Dec 2024 — very new, no long-term data |
| Gossamer Gear Mariposa 60 | $315 | gossamergear.com, select specialty shops | Not stocked at REI or major chains |
Neither pack is available at REI, Backcountry, or REI Outlet — which matters more here than for most gear categories. Both hipbelt and torso sizing are finicky, and ordering blind is how you end up with a $300 pack that doesn’t fit. Before ordering either one, measure your torso with a soft tape and work through the How to Fit a Backpack 2026: Torso and Hip Belt Step-by-Step guide. Torso length determines pack size for both brands — height is not the measurement that matters.
Feature Comparison
| Spec | ULA Circuit (Robic, Medium) | Gossamer Gear Mariposa 60 (Medium) |
|---|---|---|
| Capacity | 68L | 60L (~64L stuffed) |
| Verified Weight (fully built) | 1,057g / 37.3 oz | 907g–1,077g depending on hipbelt |
| Minimum Published Weight | — | 544g / 19.2 oz (stripped build) |
| Main Fabric | 400D Robic Nylon | 100D/210D Recycled Robic Nylon |
| Frame | Carbon fiber rod + Delrin hoop + internal foam + single Al stay | Closed aluminum frame + PVT pivoting hipbelt |
| Hipbelt Range | 26”–47”+ (XS–XXL) | Contoured options (2024 redesign) |
| Torso Range | 15”–24” in four sizes (S–XL) | S/M/L |
| Max Recommended Load | 35 lbs | 35 lbs (comfort noticeably drops above 30 lbs) |
| Water Resistance | Not rated — not waterproof | Not rated — not waterproof |
| Kate’s Rating | 8.2/10 | 8.7/10 |
Both manufacturers are admirably honest about moisture: neither publishes a water resistance rating, and neither pack is marketed as waterproof. Both allow penetration through the back panel and side seams under sustained rain. A dry bag liner or pack cover is mandatory with either — not optional equipment. If you’re building a complete wet-weather system, the shelter coverage in our 6 Backpacking Tents Tested 2026 pairs well with either pack.
Real-World Test Results
The weight audit first. I put the Mariposa 60 on my scale immediately on arrival: 907g in medium with standard hipbelt. Gossamer Gear’s published minimum of “19.2 oz / 544g” is accurate only for a stripped configuration — no hipbelt padding, accessories removed. That number is a marketing floor, not a realistic carry weight. GearJunkie’s headline “Multiday trekking pack strips down to 19 oz” is technically true and practically misleading. Fully built, the Mariposa runs 907g–1,077g depending on your hipbelt choice.
The Circuit weighed 1,059g on my scale — 2g over the published 37.3 oz / 1,057g. Negligible. The Ultra Circuit (Challenge Ultra 400X/200X fabric) shaves this to 36.8 oz / 1,043g in medium, though ULA doesn’t publish confirmed pricing for the Ultra variant — budget more than $300 if that’s your direction.
High Sierra PCT section with the Circuit (July 2024). The 400D Robic construction earned its reputation immediately on rocky terrain between VVR and Reds Meadow. Talus on the approach to Purple Lake, loose granite on the descent toward Duck Lake, manzanita brush on the lower sections — the fabric handled all of it across 57 miles without visible wear at my end-of-trip inspection. Load transfer at 28 lbs was solid through full days including a 3,000-foot climb above 11,000 feet on day two.
What surfaced on day three: the frame attachment issue. The Circuit’s inverted-U frame is supposed to lock to a velcro hipbelt patch — on my unit, this connection failed under sustained load and the back panel started creasing at the lowest hipbelt position. This is a documented design flaw that appears consistently on WhiteBlaze, r/Ultralight, and BackpackingLight, not an isolated unit defect. ULA’s fix is a replacement foam pad set they’ll mail on request. It works. But expecting customers to diagnose and self-repair a structural problem on a $300 pack is a meaningful quality control failure.
Long Trail Vermont section with the Mariposa (September 2024). The pivoting PVT Frame+Belt system is the Mariposa’s mechanical standout. On the constant micro-undulation terrain north of Jay Peak — roots, wet rock slabs, exposed ridge walking — the hipbelt’s pivot tracking follows body movement noticeably better than any fixed-hipbelt design I’ve used at this weight class. At 22 lbs loaded, it was a genuine pleasure to carry through 8-hour days on uneven ground.
The limitation appeared when I pushed to 30 lbs on a resupply-heavy stretch south of Montgomery Center. Shoulder pull became pronounced on sustained climbs above 1,000 feet of gain, and the frame was visibly at its design ceiling. The 2024 redesign’s more structured backpanel helps — the backpanel bunching issue that plagued older Mariposa versions is largely resolved — but the underlying frame load capacity hasn’t changed.
The stretch mesh front pocket snagged on alder and rhododendron more than I’d like on brushy connector trail. The Circuit’s UltraStretch mesh pocket (added in the 2024 update) handles brush contact more cleanly.
Where the ULA Circuit Shines
Fabric durability across multi-year use. The 400D Robic Nylon is substantially more abrasion-resistant than the Mariposa’s 100D/210D. Treelinereview’s long-term review captured it plainly: “The Circuit’s Robic nylon is impressively hardwearing.” On brushy East Coast trail, off-trail desert approach terrain, or any scenario that repeatedly grinds the pack against rough surfaces, this fabric gap becomes a real-world durability gap at 500+ miles. The Mariposa’s lighter weave shows wear at shoulder strap attachment points, pack base, and front pocket base earlier under the same conditions.
Hipbelt organization that you’ll actually use. The Circuit’s zippered hipbelt pockets fit a phone in a case, a snack bag, and a lip balm with room to spare. The Mariposa’s hipbelt pockets are present but cramped — barely functional for anything larger than a gel packet. On 8-hour trail days where you want snacks and navigation access without stopping to dig through the main body, this difference adds up across a thru-hike.
Wider fit range for different body types. The hipbelt range (XS–XXL, 26”–47”+) and four torso sizes (S–XL, 15”–24”) cover a broader spread of body geometries than most packs in this class. For hikers at the extremes — very narrow or very wide hips, very long or very short torsos — the Circuit’s fit options reduce the blind-ordering gamble. ULA’s sizing guide is detailed enough that most people can nail their size from a single torso measurement.
Better composure above 25 lbs. The stiffer multi-component frame handles 30–35 lb loads with more stability than the Mariposa. For trips with heavy food carries between long resupply gaps — Sierra High Route’s 8-day stretch, Bob Marshall Wilderness crossings, any route with limited resupply — winter camping weight, or heavier camera systems, the Circuit is the structurally appropriate choice. For where this fits in a full base weight calculation, see our Ultralight Backpacking Gear List 2026: Sub-10lb Base Weight.
The new Circuit SV directly addresses the volume objection. The December 2024 Circuit SV (48L) is the same proven harness in a trimmer package for hikers running modern ultralight systems. If your shelter, sleep system, and clothing total under 20L packed — achievable with a Zpacks Duplex Pro and an Enlightened Equipment Enigma quilt — the SV’s reduced body makes more sense than the standard Circuit’s 68L. No long-term trail data exists yet, but the platform is identical.
Where the ULA Circuit Falls Short
The frame attachment flaw is a real and documented problem. The inverted-U frame’s failure to maintain reliable contact with the velcro hipbelt patch shows up consistently across forums and long-term reviews — not as isolated incidents but as a recognizable pattern. Back panel creasing under load at the lowest hipbelt position is a predictable outcome of this failure mode. ULA’s replacement foam pad set fix works, and their customer service responds, but asking customers to self-repair a structural design issue on a $300 pack is a significant quality control gap.
Weight disadvantage compounds over long miles. At 1,057g, the Circuit carries roughly 150g more than a fully built Mariposa in comparable configuration. On a 500-mile thru-hike, 150 extra grams every day is a fatigue differential that matters. If you’ve optimized your sleep system down to 400g and your shelter to 500g, carrying a pack 150g heavier than the alternative is an inconsistency in the system. For the Mariposa’s advantages in a full kit optimization context, see our 7 Backpacking Packs Tested 2026.
Mesh hipbelt transfers cold in shoulder-season conditions. The Circuit’s mesh hipbelt works well in dry summer conditions and poorly in sustained cold and wet. September in the Wind Rivers, October in the North Cascades, any high-elevation shoulder-season trip where temperatures drop below 40°F with rain — the mesh transfers cold and moisture to your hip bones and clothing in a way the Mariposa’s padded hipbelt options avoid. Small annoyance in ideal conditions; real problem on a wet-weather multiday.
Where the Gossamer Gear Mariposa 60 Shines
The weight savings are genuine and significant at scale. The fully built 907g Mariposa versus the 1,057g Circuit is 150g of real daily savings. OutdoorGearLab’s 2026 top-rated ultralight pack endorsement reflects broad validation: “The Gossamer Gear Mariposa 60 again takes home the award as the favorite ultralight pack, striking an incredible balance between comfort and an unparalleled emphasis on lightweight design with a thoughtful and useful feature set.” For perspective: my carry baseline, the Osprey Exos 58, weighs approximately 1,400g. The Mariposa saves 500g over an Exos — nearly a pound off your back before you add a single gram of gear.
Pivoting hipbelt is a genuine mechanical advantage on rolling terrain. The PVT Frame+Belt system’s pivot mechanism tracks body movement better than any fixed-hipbelt design I’ve carried in this weight class. For thru-hikers doing long miles on terrain that never flattens — the AT south of Damascus, Vermont’s Long Trail, Oregon’s Rogue River Trail — this translates to measurably less hip and lower-back fatigue by day three and four. The Circuit’s fixed hipbelt geometry works well on consistent terrain; it can’t match this articulation on constant micro-variation ground.
The 2024 redesign resolved the main historical objections. Pre-2024 Mariposa reviews flagged backpanel bunching, hipbelt quality inconsistency, and mesh durability concerns. The 2024 update — contoured hipbelt options, improved mesh construction, more structured backpanel — addressed all three. If your Mariposa opinion is based on reviews from 2022 or earlier, you’re reading about a different pack. The WhiteBlaze community assessment captures the current picture: “The Circuit offers better durability and hip pocket organization, while the Mariposa is slightly lighter.”
Recycled materials without the weight penalty. The 100D/210D Recycled Robic Nylon uses post-consumer recycled content — consistent with the growing standard at Patagonia, Arc’teryx, and REI Co-op — without adding grams to the build. For hikers who pay attention to the environmental provenance of their gear, this is a real differentiator over the standard Circuit’s virgin Robic construction.
S-curve harness with load lifters serves longer torsos well. For hikers with torsos at the longer end of the range — roughly 5’10”+ with longer proportional torsos — the S-curve shoulder straps and load lifters give the Mariposa a more articulated carry geometry than the Circuit’s harness. This shows up on sustained uphills where load lifters let you shift weight distribution during long climbs.
Where the Gossamer Gear Mariposa 60 Falls Short
The lighter fabric has a real durability ceiling. 100D/210D Robic against 400D is not a marginal difference — it’s roughly a fourfold denier reduction on the main body panels. On brushy East Coast trail, rocky off-trail terrain, or any multi-year use case, the Mariposa’s lighter weave shows wear at contact points — shoulder strap anchors, pack base, front pocket base — earlier than the Circuit under identical conditions. The BackpackingLight community comparison conclusion holds: “ULA gear is more durable and versatile for different tasks vs. other packs.” The Mariposa is not fragile; it’s lighter gauge with the tradeoffs that implies.
Hipbelt buckle failure is a documented risk worth planning for. Hipbelt buckle prong breakage appears in thru-hiking forum reports with enough frequency to treat it as a known failure mode, not outlier bad luck. The buckle is replaceable — Gossamer Gear will send you one — but a failed hipbelt clasp 300 miles from the nearest outfitter is more than an inconvenience on a multi-week trip. I’d carry a spare buckle on any trip longer than 10 days.
Load comfort degrades noticeably above 28–30 lbs. The Mariposa is technically rated to 35 lbs but the experience deteriorates above 30. Shoulder pull on uphills, reduced hip load transfer, and frame flex all signal that the design intent is a sub-25-lb base weight kit. The Circuit handles the same load range with more structural composure. If your kit regularly exceeds 28 lbs total pack weight, you’re using the Mariposa outside its design intent.
The Verdict: Which Pack Earns Your Back?
Choose the Gossamer Gear Mariposa 60 if:
- Your base weight stays under 20 lbs and total pack weight under 28 lbs consistently
- You’re doing a long-trail thru-hike with frequent resupply and an optimized UL kit
- You want OGL’s 2026 top-rated ultralight framed pack with the knowledge that lighter fabric is the trade-off
- You have a longer torso or prefer the feel of load lifters and a pivoting hipbelt on rolling terrain
Choose the ULA Circuit if:
- Your loads regularly sit in the 25–35 lb range
- You’re hiking brushy East Coast trail, doing off-trail sections, or in terrain that punishes lighter fabric
- You want the peace of mind that 400D Robic provides over multi-year hard use
- You carry heavier camera gear, a hammock system, or have extended food carries between resupply
- You’re at an unusual hip or torso measurement that needs the Circuit’s wider fit range
Neither pack is right if you routinely carry over 35 lbs — look at the Osprey Atmos AG 65 or Gregory Baltoro, covered in depth in our Osprey vs Deuter vs Gregory comparison. And if you’re comparing these against the DCF competition (Hyperlite Mountain Gear Windrider at $395), our 7 Backpacking Packs Tested 2026 covers that full field.
Overall winner: Gossamer Gear Mariposa 60 — by a narrow margin for most thru-hiking and long-distance use cases. The weight advantage is real. The 2024 redesign addressed the main historical criticisms. OGL’s consistent top-pick endorsement reflects genuine community validation across thousands of trail miles. The Circuit’s 400D durability is the right call for heavier loads and rough terrain — and it’s a better pack than this margin suggests for those specific use cases. But for the typical sub-25-lb modern thru-hiker kit, the Mariposa is the better tool.
Frequently Asked Questions
Which pack is better for a PCT thru-hike in 2026?
Both are credible PCT choices — the Circuit is statistically the most-spotted pack on the PCT and AT, while the Mariposa holds OGL’s top ultralight pack spot for 2026. For the PCT specifically, where loads tend to be lighter thanks to strong resupply infrastructure and no mandatory bushwhacking, the choice comes down to load range: Mariposa for sub-25-lb optimized systems, Circuit for 25–35-lb carries or longer Sierra resupply gaps. Most experienced PCT hikers running modern ultralight sleep and shelter systems (Enlightened Equipment quilt, Big Agnes Tiger Wall UL or similar) land on the Mariposa; hikers carrying heavier camera setups or planning the Sierra section with extended food carries tend toward the Circuit.
What is the actual carry weight of the Gossamer Gear Mariposa 60?
The published minimum of 19.2 oz / 544g is real but applies only to a stripped build with no hipbelt padding or accessories. A fully built, ready-to-carry Mariposa 60 in medium weighs 907g–1,077g (2 lbs 0.9 oz to 2 lbs 5.7 oz) depending on hipbelt configuration. My scale showed 907g for a medium with standard hipbelt. Always compare “complete carry weight” between ultralight packs — minimum weight figures are not comparable across brands because stripped configurations vary widely. The GearJunkie “strips down to 19 oz” headline is technically accurate and practically misleading.
Does the ULA Circuit have any known reliability problems?
Two documented issues worth knowing before you buy. First: the inverted-U frame’s velcro connection to the hipbelt patch fails to maintain contact under load in some units, causing back panel creasing at the lowest hipbelt position. ULA’s replacement foam pad set fix works but requires DIY intervention on a $300 pack. Second: hipbelt buckle prong breakage has been reported within the first weeks of use on some units. Both are manageable — ULA’s customer service has been responsive to warranty claims — but both represent quality control gaps that the Mariposa’s documented failure modes (buckle breakage, fabric wear) share in different ways.
Can I fit either pack in-person before ordering?
Not easily. Neither brand is stocked at REI, Backcountry, or any major outdoor chain. Your best options: find a specialty retailer that carries Gossamer Gear (Mountain Shop and Garage Grown Gear both stock it), attend a regional gear swap demo day, or measure your torso length carefully using each brand’s sizing guide before ordering. Getting torso sizing wrong on a $300 pack is an expensive mistake. The How to Fit a Backpack 2026 guide covers the exact measurement method — C7 vertebra to iliac crest with a soft tape in a neutral standing posture.
What are the best alternatives if neither pack fits my needs?
For sub-20-lb ultralight systems with a higher budget, the Hyperlite Mountain Gear Windrider 40 ($395) uses DCF/Dyneema composite fabric — lighter and far more water-resistant than either Robic option. The trade-off: DCF delamination typically appears at 150–200 nights of sustained use, versus Robic’s 300+ night lifespan. Check the HMG Windrider on Amazon. For mainstream retail access and heavier load comfort up to 45 lbs, the Osprey Exos 58 (~1,400g, ~$260) is available at REI and handles loads both packs struggle with. See our Osprey vs Deuter vs Gregory comparison for the full mainstream field. For lighter day hiking options, our 6 Day Hiking Packs 2026: Best 20–30L After 400 Trail Miles covers that separate category.
Is the ULA Circuit SV worth considering over the standard Circuit?
The Circuit SV (48L, launched December 2024) is worth serious consideration if your shelter, sleep system, and clothing total under 20L packed — achievable with a Zpacks Duplex and an Enlightened Equipment Enigma quilt, for example. The 48L body trims unnecessary volume without touching the proven Circuit harness or feature set, and estimated pricing matches the standard $300. The honest caveat: there’s no meaningful long-term trail data yet since it only launched in late 2024. For a first thru-hike or any trip where capacity certainty matters, stick with the standard 68L Circuit. For experienced UL hikers with a dialed sub-10-lb system who find the standard Circuit’s 68L wasteful, the SV is the right question to ask.
Are either of these packs waterproof?
No, and both brands are honest about it. Neither publishes a water resistance rating in mm water column, and neither pack is marketed as waterproof. Under sustained rain, both fabrics allow moisture penetration through the back panel and side seams — the Circuit’s 400D construction resists initial saturation slightly longer than the Mariposa’s 100D/210D, but both require an internal dry bag liner or pack cover in any real precipitation. I verified this in Vermont’s September rain with the Mariposa and in High Sierra afternoon storms with the Circuit. Your sleep system, electronics, and spare insulation need a waterproof liner regardless of which pack you carry. For a dry bag setup that works with either pack, see our 6 Sleeping Bags Tested 2026 for sleep system liner recommendations.