Golite Infinity at Davis Lake
Alan wearing a GoLite Infinity at the top of a 13,000 foot (4,000 m) col in the High Sierras. The Infinity is one of our favorite light packs for alpine rock and ice travel, summit attempts, and winter ski trips. It is a heck of a solid trail pack, too.


In the world of backpacking, framed packs are the norm. And why shouldn’t they be? Most backpackers carry loads that need the comfort and support of a framed pack. But framed packs have only recently become lightweight. For years, when carrying the 30 to 40 pounds (14 – 18 kg) necessary for an alpine, desert or winter backpacking trip, many lightweight backpackers have extended the carrying capacity of our frameless packs by increasing our tolerance to pain. Relief is here. As interest has grown in lighter weight packs, more manufacturers are producing internal framed packs that can comfortably handle 30 to 40 pounds (or more) but weigh substantially less than the 5 to 8 pounds (2.3 – 3.6 kg) of their heavier and older cousins.

As lightweight backpackers, we are interested in framed packs that comfortably carry between 20 to 40 pounds (9 – 18 kg). With good lightweight equipment choices, one can do an extended winter ski trip or a long dry stretch of desert travel with a loaded pack weighing somewhere in this range. In fact, it is hard to think of a trip (short of climbing) where a lightweight backpacker would carry much more than 35 pounds (16 kg).

Though it has been the industry standard for over a decade, it is not written in stone that a pack frame must consist of two aluminum stays running along an HDPE plastic framesheet. In the last few years we’ve seen other frame designs with similar torso flexibility and load carrying performance that weigh less. GoLite takes an innovative step in this direction with their Unlimited pack series. They use a corrugated polystyrene framesheet supported by small diameter, 7075 aluminum rods inserted through the corrugations. This framesheet is similar to the material used by the U.S. Postal Service in their white mail crates; and, like the mail crates, GoLite’s framesheet does an excellent job of supporting weight. We reviewed the 39.5 ounce (1,120 g) GoLite Infinity from this series, which comfortably carries 40 pound (18 kg) loads!

Granite Gear Vapor Trail somewhere
Combining excellent fit, especially for women, with solid construction and superb load carrying capacity, the Granite Gear Vapor Trail is among our favorite full-featured packs for on-trail and modest off-trail travel. Alison is shown here crossing a summer snowfield enroute to a high alpine col.

Lightweight framed packs have borrowed from the design evolution of ultralight frameless packs. Now many internal frame packs also incorporate “virtual frame” components into their pack design to improve load-carrying capability. Some of the lightest framed packs have exceptional virtual frames, allowing them to reduce frame weight while maintaining rigidity through the combined internal frame and virtual frame. Granite Gear’s 32.2 ounce (913 g) Vapor Trail has only a thin and somewhat flexible HDPE framesheet for a frame. However, because it has a comprehensive compression system to create a good virtual frame, it carries 30 pounds (14 kg) in total comfort. We also like the frame innovation employed by Gossamer Gear (formerly GVP Gear) in their new 17.0 ounce (482 g) Mariposa pack. The Mariposa combines the support of a folded sleeping pad inserted into the backpanel with two, extremely light (0.9 oz (26 g)/pair), carbon fiber rods to create a frame also suited to 30-pound loads.

The above examples represent some of the more innovative approaches to frame design. Although aluminum stays and HDPE plastic framesheets are still common, even these have undergone improvements. Mountainsmith has replaced the common bar-stock aluminum stays with corrugated stays (which are shaped like the wavy middle layer of corrugated cardboard with the corrugations running the length of the stays). Because the corrugations add stiffness to the aluminum, the stays can be made using thinner and lighter aluminum. We reviewed the Mountainsmith Auspex, which uses two such corrugated stays. This pack weighs in at 65.3 ounces (1,851 g), which seems rather heavy until you consider its 65-pound (30 kg) carrying capacity. We are also seeing hollow aluminum stays in a number of packs. Gregory uses a hollow aluminum stay to create a comfortable frame and harness in their G Pack which weighs 43.6 ounces (1,236 g) with a 30 pound (14 kg) carry capacity.

As with our Frameless Pack Reviews, comfortable carry ratings for internal frame backpacks are as tricky and subjective as sleeping bag ratings. With framed packs, torso collapse is less of a concern than it is for frameless packs. What matters more for comfort are the components of a framed pack’s harness, fit, adjustability, and the user’s tolerance to carrying weight. It is the user’s tolerance that tends to introduce the most subjectivity. We do all we can to eliminate this by extensively testing our packs while carrying various weights and volumes over both smooth and rough terrain. We then discuss and debate our comfort findings with other Backpacking Light staff members and make necessary adjustments to normalize our results to suit the average user. Nevertheless, you might find our comfort ratings a little higher or lower than your own depending on your own preferences.

Because a framed pack is capable of carrying heavier loads, and may be employed to carry climbing or alpine gear as well, fabric selection is important and often defines how the pack can be used. For example, Gossamer Gear’s Mariposa, which uses 1.3 oz/yd2 (44 g/m2) silnylon for most of the pack body, is a super light pack that may be an excellent choice for an ultra-light backpacking trip, but it is not suited to more abrasive backcountry pursuits. Fabrics have improved dramatically over the last several years. Long gone are the days where one had only to decide between 500 and 1,000 denier Cordura for their entire pack. Now, a single pack typically has several types and weights of fabric. To reduce weight, manufacturers tend to use heavier and more durable fabric only in high wear areas like the pack bottom and use lighter fabrics in less abused areas like the top of the back. We separate a pack’s fabric selection into two classes, ultralight and lightweight. In some instances a pack containing ultralight fabrics may weigh more due to a heavier harness and/or frame.

Gossamer Gear Mariposa somewhere
Jay and the Gossamer Gear Mariposa in the Bear Wallow Wilderness in eastern Arizona. At only 17 ounces (480 g) and with carbon fiber stays, it is the ultimate in light packs for hikers who travel long on-trail distances.

Packs in an “ultralight fabric class” generally use various weights of silnylon ripstops (ranging from 1.3 oz/yd2 to about 2.4 oz/yd2 (44 – 81 g/m2)) through the pack body and heavier weight fabrics in high wear or high stress areas. These heavier weight fabrics can be as light as 1.9 oz/yd2 (64 g/m2) urethane coated ripstop nylon, to much more abrasion resistant 6.5 oz/yd2 (221 g/m2) high tenacity Cordura. Framed packs that fit into this class include the Gregory G Pack, Camelbak Kronos, Gossamer Gear Mariposa, and all the Ultralight Granite Gear packs. Although these packs represent lightweight ideals in fabric selection, we found the upper portion of all these packs more susceptible to abrasion damage. These would not be a first choice for bushwhacking or climbing where encounters with brush or rock would be frequent.

Packs in a “lightweight fabric class” use more durable fabrics and handle light bushwhacking and climbing. Although various weights of Cordura, pack cloth, and ripstop nylons are commonly used in this class for different areas of the packs, some specialty fabrics have made a huge impact to this class. Dimension Polyant X-Pac fabric, used in GoLite’s Infinity and Mountainsmith’s Auspex packs, features a three layer construction consisting of an outer 40 denier polyester bonded to a 1,000 denier high tenacity polyester matrix with a 50 denier polyester liner. The 1,000 denier high tenacity fiber is highly load bearing and tear resistant creating a superior fabric at only 3 oz/yd2 (102 g/m2). Another fabric is Dyneema Gridstop, used in Mont-Bell’s Alpine series, ULA’s entire pack line, and several packs from GoLite. The fabric consists of 210 denier high tenacity nylon with a 215 denier gridstop of Dyneema fiber. Dyneema is nearly identical to Spectra in terms of strength (pound for pound twice as strong as Kevlar and 10 times as strong as steel) and the fiber is light enough to float on water, creating a final gridstop pack cloth weighing 4.5 oz/yd2 (153 g/m2).

The combination of lightweight frames/harnesses and lightweight fabrics has pushed the envelope of what a 2 to 4 pound (0.9 – 1.8 kg) pack can do. The term “lightweight” can now be used in the same sentence with “expedition.” Innovations that were once found only in ultralight and lightweight packs have now found their way into the designs of large volume, higher carrying capacity packs. ULA’s P-2 demonstrated carrying capacities of 35 to 40 pounds (16 – 18 kg) and 4,900 cubic inches (80 L) with a weight under 3 pounds (1.4 kg). For even greater loads, say for a winter summit ascent requiring ice axes, crampons, and the like, the Mountainsmith Auspex can comfortably handle 60 pounds (27 kg) of gear (4,000 ci, 66 L) at a weight of 4.1 pounds (1.9 kg). Though the Auspex is by no means a featherweight, it is still respectable considering the market standard weight for a pack capable of carrying such loads starts around 6 pounds (2.7 kg) and goes quickly up from there.

Some will wonder if an ultralight pack can carry all the accessory gear of their heavier cousins. Out of all the packs Backpacking Light has tested, Osprey’s Aether 60 (56.6 oz, 1,605 g) comes closest to a do-it-all pack. Not only does it have attachment options for skis, snowboards, snowshoes, ice axes, climbing ropes, and much more, the attachment points are durable and easily employed. These options were not afterthoughts with the Aether 60, but are integrated cleanly into the pack’s overall design. This pack can comfortably carry 35 pounds (16 kg) which means it can carry several of these items along with a few days worth of camping gear. For week-long or winter trips, some of our reviewers would use an Aether 60, even though it weighed more than other packs with similar volumes and load carrying capacity because of its integrated attachment options.

Framed Pack Ratings Chart for Packs Reviewed by Backpacking Light
Mfr / Model Frame Features Volume Range Load Carrying Durability Value Average Score
Camelbak Kronos 3.5 4 3.5 4.5 2.5 3.5 3.1
GoLite Infinity 5 5 4 5 4.5 4 4.0
Gossamer Gear Mariposa
3.5 4 2.5 4 2 3.5 3.4
Granite Gear Nimbus Latitude 4.5 3.5 5 4.5 3.5 3.5 3.3
Granite Gear Nimbus Ozone 4.5 3.5 5 4.5 3.5 3..5 3.5
Granite Gear Vapor Trail 4 3.5 5 3.5 3.5 4 3.6
Gregory G pack 4.5 2.5 3 4.5 2.5 2.5 2.9
Mont-Bell Alpine 60 4.5 4 3 4.5 4 3.5 3.2
Mountainsmith Auspex 4.5 4.5 4 5 5 4 3.8
Osprey Aether 60 4 4.5 5 4 5 4 3.5
ULA P-2 4 4 3 4.5 4 4.5 3.4
Mfr / Model Weight
oz (g)
ci (L)
Volume / Weight
Carrying Capacity
lbs (kg)
Capacity / Weight
Cost ($)
Camelbak Kronos 50.9 (1,443) 2420 (40) 48 35 (16) 11 130
GoLite Infinity (size L) 39.5 (1,120) 3250 (53) 82 40 (18) 16 199
Gossamer Gear Mariposa
17.0 (482) 4200 (69) 247 30 (14) 28 140
Granite Gear Nimbus Latitude 56.8 (1,610) 3800 (62) 67 40 (18) 11 230
Granite Gear Nimbus Ozone 48.7 (1,381) 3800 (62) 78 40 (18) 13 200
Granite Gear Vapor Trail (size Short) 32.2 (913) 3300 (54) 102 35 (16) 17 150
Gregory G pack 43.6 (1,236) 2900 (48) 67 30 (14) 11 149
Mont-Bell Alpine 60 59.6 (1,690) 3050 (50) 51 40 (18) 11 179
Mountainsmith Auspex (size LT) 65.3 (1,851) 4000 (66) 61 65 (30) 16 230
Osprey Aether 60 56.6 (1,605) 3700 (61) 65 35 (16) 10 199
ULA P-2 47.2 (1,338) 4900 (80) 104 35 (16) 12 210

The Framed Pack Ratings Chart summarizes the ratings from the various framed packs we have reviewed to date. Packs are size Medium (if there is an option) unless otherwise noted. Though we have included an average score for each pack, don’t overlook specific ratings for each category. Use only as much pack as you need. Don’t buy a highly rated pack that can carry up to 60 pounds (27 kg) if you expect to carry less than 30 pounds (14 kg). The Gossamer Gear Mariposa scores in the middle of the pack. However, its 17-ounce (482 g) weight and load carrying capacity make it ideal for 20 to 30 pound (9 -14 kg) loads on the open trail. If you’re a hiker that carries low volume loads and/or under 30 pounds in weight on the trail, don’t be seduced by large volume, ultra durable and/or high carry capacity packs. The Mountainsmith Auspex, which had the highest carrying capacity and performs exceptionally for heavy, high volume loads, weighs nearly twice that of many packs that comfortably carry 20-40 pounds (9 – 18 kg) – the loads most lightweight backpackers carry. Bottom line: pick the lightest pack that meets your needs.

The average score summarizes all ratings except for cost. The values for Weight were normalized to a 1 to 5 scale (from a value of 1 for 65.3 ounces (1,851 g) to a value of 5 for 17.0 ounces (482 g)) and given double averaging weight. The values for Carrying Capacity were also normalized to a 1 to 5 scale (from a value of 1 for 30 pounds (14 kg) to a value of 5 for 65 pounds (30 kg)) and given single averaging weight. Unless otherwise indicated in the header row, ratings are on a scale of 1 to 5, with 5 being the best.

BackpackingLight.com Gear Guide to Internal Frame Backpacks

Click here for the index

Gear Guide Selection Criteria

  • Framed packs: packs that have something harder and stiffer than closed cell foam in the backpanel. We have included packs with plastic framesheets in our framed packs
  • Pack volume exceeds 2,000 cubic inches (33 L)
  • Pack volume to weight ratio is greater than 50 cubic inches per ounce for packs with less than 4,000 cubic inch volumes and greater than 60 cubic inches per ounce for packs with greater than 4,000 cubic inch volumes, based on manufacturer provided volume and weight

Note: Inclusion criteria assumes volumes and weights in a size medium.

2004 BackpackingLight.com Internal Frame Backpack Reviews – Explanation of Review Criteria


Though most of the specifications are self-explanatory, the following need quantifying:

  • Volume to Weight Ratio This value was used in the selection process for the framed packs. It is derived by dividing the pack volume by the Backpacking Light-measured weight and expressed in units of cubic inch per ounce. This number provides a basis for comparison of different packs with different volumes by lessening the effect change of volume has on pack weight. This value can suggest how efficiently a manufacturer used materials to reduce weight in comparison to other packs. Do not equate this value with performance, as there are ways to reduce pack weight that will negatively affect one’s desire to carry the pack. In other words, better (higher) values do not necessarily suggest a better pack, as many factors go into pack performance and carry comfort. However, a highly rated pack with a high volume to weight ratio suggests the manufacturer was able to maintain high levels of comfort while minimizing weight.
  • Load Carrying Capacity – Backpacking Light tests each pack to determine the maximum comfortable load carrying capacity for most users and provides this value here along with the manufacturer’s suggested capacity when provided.
  • Carry Load to Pack Weight Performance Ratio – A unitless value derived by dividing the Backpacking Light-determined maximum load carrying capacity of the pack (pounds) by the Backpacking Light-measured pack weight (also pounds). Packs with better suspension systems and better weight transfer to the hips that carry heavier loads relative to empty pack weight will have higher ratios. Light packs, with a good frame that efficiently transfers weight to the hips, and a light but comfortable harness, will also do well in this measure. The ratio does not take into account additional – and sometimes highly desirable – features such as more durable fabric and construction, and additional pockets or a top flap. As such, it should not be considered an exact measure of performance to weight unless comparing packs with fairly similar designs.


Ratings follow subtitles on a scale of 1 to 5, with 5 being the best, and are relative to other framed packs tested by Backpacking Light.

Frame and Suspension

Here we describe the components of the frame and suspension: framesheets and stays, shoulder straps, hipbelt, sternum strap, shoulder strap stabilizers, and hip belt stabilizers. We also describe the adjustability of the suspension and harness components. If a pack has the ability to adjust to different torso sizes, that feature is also discussed.

Note: only frame and suspension features are described in this section. The load-carrying performance of the pack is evaluated in the Field Performance section.

Usable Features and Ease of Use

Here we describe the usable features of the pack (the “extras”); including but not limited to pockets, top flaps, bottle holders, hydration systems, axe loops, shock cord systems, etc. We also consider the design and use of these features, such as the type, size, location and shape of the pockets. We consider it a plus if you can reach back and get a water bottle or camera out of a side pocket without having to take the pack off. Mesh pockets are a plus since they enhance gear drying and content visibility. Hydration pockets get higher ratings if the bladder can be replaced without unpacking the main pocket of the pack. “Ease of use” considers how complicated it is to properly use a pack.

Load Volume Flexibility

This measures the pack’s ability to control larger or smaller volume loads. The need to control volume happens on long trips where you start out with a lot of food. As you consume the food your pack might end up at half its original volume. This also happens during cold weather trips: when temperatures drop, you may end up wearing a lot of high volume insulation garments that started out in your pack. Finally, you may decide to unload most of the gear in your “trail pack” and use it as a day or summit pack.


A few manufacturers offer options for their packs, such as alternate fabrics, add on pockets, hydration sleeves, padded hip belts, frame stays, etc. This section is only included for those packs that have options that need to be described.

Field Performance

Pack Load Carrying

This is an evaluation of how well the pack can carry a load. Typically, the pack is tested beyond the manufacturer’s suggested load carrying capacity and carried with progressively less weight in order to validate the manufacturer’s suggestions. This is done with the pack packed as optimally as possible so we can push the pack to its limit. If appropriate, we also evaluate how different volumes affect the “virtual frame” portion of the frame system by testing lower volume loads. Finally, we test the load stability of the pack and how this affects center of gravity.


How well did the pack hold up to abuse (e.g., scrapes against granite and brush)? Are there reinforcements or heavier fabrics in high wear areas? We describe the seams and webbing attachments. We also evaluate the durability when using the pack for off-trail or climbing use. Higher rated packs are those that have more durable fabrics in high wear areas, reinforcements, double or triple stitching, bar tacking on pack straps, etc.


This is our most subjective rating. It takes into account all of the above criteria, along with the pack’s price. Some adjustment is made for the type of pack. For example, a lower capacity, 25-ounce (709 g), webbing-belted pack with light fabric is not directly comparable to a larger capacity, 40+ ounce (1,134 g) pack with a fully padded hipbelt and heavier and more durable fabric.

2004 BackpackingLight.com Internal Frame Backpack Reviews – Index of Reviews

Manufacturer / Model

Camelback Kronos Backpack Review (pending)

M Golite Infinity Backpack Review

M Gossamer Gear Mariposa Backpack Review

Granite Gear Nimbus Latitude Backpack Review

Granite Gear Nimbus Ozone Backpack Review

M Granite Gear Vapor Trail Backpack Review

M Gregory G Pack Backpack Review

Mont-Bell Alpine 60 Backpack Review (pending)

Mountainsmith Auspex Backpack Review

Osprey Aether 60 Backpack Review

M ULA P-2 Backpack Review