As with many things in life, deciding whether to use an internal frame—or if you even need one—is subjective: it's based on how you plan to carry your backpack, what you plan to carry in it, and how carefully you're willing to pack it. A lot of folks will find an internal frame useful, but not everyone will, and certainly not everyone needs one, especially those who carry smaller/lighter packs or less gear.

Our Hero's Journey, Guide's Pack, and Guide's Edition Synapse 25 backpacks all come with internal frames included. Versions of the same internal frame are optional for our Synapse 19 and Synapse 25 backpacks. But just because we offer internal frames doesn't mean they're required; our goal with this guide is to give you the facts as we know them (experientially, theoretically, and historically) so you can make the decision as to what's best for you and your carrying comfort.

Before we really dive into this, let's start off making sure we're all on the same page with the definitions:

External Frame
Many of the first “modern” outdoor packs (starting in the 1960s) utilized an external frame made of tubular aircraft aluminum – basically a lighter version of the old Trapper Nelson wood frame. The innovative addition of a padded hip belt allowed the user to transfer most of the load to their hips. The bag was generally packed with the heavy stuff up high, so the center of gravity could more easily shift to be over the hips. The rigidity of the frame allowed a fabric or mesh back panel to be stretched across it, creating air circulation between the pack and the user’s back. These packs were, and still are, very good for carrying heavy loads on relatively even trails. Off trail or cross-country travel was less fun, as that same high center of gravity became unwieldy with any sort of athletic jumping or clambering around.

Internal Frame
In the early 1970’s, manufacturers began introducing internal frame packs, hoping they could make something that performed better for high mountain and off-trail travel than rigid external frame packs. Many folks found these new packs to be a happy medium between clunky external frames and completely soft frameless packs. There have been numerous variations of internal frames developed over the years, some made of fiberglass, some plastic, some consisting only of one or two aluminum stays. Our version basically takes a frame sheet (see below) and adds a single bendable aluminum stay. Properly bent and shaped to conform to one's spine, an internal frame (in this case, internal frame = frame sheet + aluminum stay) provides a degree of vertical stability that a simple frame sheet won’t, allowing one to lift some of a pack’s weight off the shoulders and onto the hips (even with just a 1″ webbing waist belt or a padded hip belt). This is in addition to the two benefits offered by a frame sheet: prevention of an overstuffed bag barreling out and a created barrier between pointy objects and the user's back. Some users also like the way the stiffness of a pack with an internal frame can make it easier to load, as the pack won’t schlump over when it’s not on your back.

Frame Sheet
A “frame sheet” is a piece of thin plastic (something along the lines of what a milk jug is made from) that rides inside the backpack, against the back, separated from the user typically by some foam padding. The idea is that with a frame sheet, you needn’t be so concerned about hard or pointy objects in your pack poking through the foam padding and causing discomfort, plus your bag will be less likely to round off and become a beer barrel when over stuffed. Because a frame sheet doesn’t add significant vertical stability or rigidity, whether used with a hip belt or not, a frame sheet won’t do much to transfer the weight of the pack onto the user's hips.

Frameless Pack
A pack without a frame sheet or internal frame. A frameless pack might even lack padding on the back panel (ala our Daylight Backpack) or it could have back padding and mesh (like our Brain Bag backpack). Some people choose to carry a large volume backpacking pack that entirely lacks any internal frame or frame sheet – see the Jensen Pack. Carefully and mindfully packing a frameless pack is an opportunity to save weight: the gear you carry serves as the support and maybe even the padding too.

Plate from Light Weight Camping Equipment and How to Make It by Gerry Cunningham and Margaret Hansson.

Original Trapper Nelson wood pack frame, circa 1950s.

Early 1960's Gerry aluminum pack frame -- note the unpadded webbing hip belt.

Early internal frame -- this one on an Alp Sport climbing rucksack.

Corduroy back panel of a frameless Jensen Pack.

Tom and Nik work on the internal frame for the Synapse: the evolution continues.

Synapse internal frame with our unique T-bar attachment.

Benefits of an Internal Frame

• On bags with a webbing or padded hip belt, the vertical stability facilitated by an internal frame with an aluminum stay can help to lift some of the pack’s weight on to one's hips.

• It creates a hard back panel that prevents less-than-carefully packed objects like a thermos or DSLR from poking one in the back.

• It can prevent an overstuffed bag from barreling out against one's back.

• To some folks, a rigid frame against their back (with padding between the frame and their pack) just feels right.

Why You Might Not Want to Use a Frame

• A frame adds weight to a bag. Our Synapse 25 internal frame weighs 9.6 oz / 272 grams and our Synapse 19 internal frame weighs 6.9 oz / 195 grams. In many cases, you can save the weight of a frame with careful and thoughtful packing.

• The rigidity offered by the internal frame becomes a liability when you’re squeezing your pack into the overhead compartment or under the seat in front of you, or when you’re packing your backpack inside other luggage. (This is one of the reasons we design our internal frames to be removable.)

• Some folks simply prefer the feeling of a frameless or soft-back pack.

The TOM BIHN Approach to Internal Frames
Make them true internal frames with an aluminum stay, and make them optional.

In case you’ve just tuned into this station, we here at TOM BIHN have always advocated for exercising thoughtfulness when packing, taking care to pad some objects by wrapping them in clothing, and positioning others inside your pack just so for optimal carrying comfort. While this somewhat monastic approach to packing certainly has some acolytes, there are as always apostates as well, and thus we’ve had more than a few requests to offer a frame sheet option with our backpacks. Each of us pack differently, and paying attention to those differences helps us design options to meet the needs of the user, whether they're a careful packer (like Tom) or more of a throw-it-in-and-go packer (like Darcy).

With this in mind, we designed a light and simple internal frame, originally for The Guide’s Pack, and then modified for the Hero’s Journey. So far so good. However, some of our customers, who, like us, seem never able to leave well enough alone, requested some sort of similar frame for our other packs. So there you have it: we’ve gone ahead and done it, and are now offering internal frames for the Synapse 19 and the Synapse 25 (as well as the Guide's Edition Synapse 25).

They all feature the same basic materials and construction as the internal frames we’ve been making since 2015: die-cut .055” thick High Density Polyethylene (HDPE), with a nylon webbing sleeve sewn down the center, encasing a 1” /25mm wide 6061 aluminum stay. In all cases we’ve bent the stay to a generic spinal curve: we recommend you re-bend and/or adjust the curvature to best fit your own back. The stay is removable, in the unlikely case you are still an unbeliever and just want a frame sheet.

Both The Guide’s Pack and the Hero’s Journey are designed specifically to accept their purpose-built internal frames, with “pockets” in the lining to accept the lobes of their respective frames. Because the Synapses were not originally intended to accommodate an internal frame, they lack any particular allowance for the attachment of such a frame, and some modifications to the frame design were required. We took advantage of the loops for the Cache rails system to allow for retaining the internal frame inside the tops of those packs: a clever “T” bar holds the frame in place relative to the loops. (Watch this video to see how it works.)The lower edge of the internal frame floats free in the Synapses—we’ve found this isn’t much of an issue as the contents of the bag tend to hold this lower extreme in place.

These TOM BIHN bags include (come with) a removable internal frame with aluminum stay:
The Guide's Pack
Guide's Edition Synapse 25
Hero's Journey

These TOM BIHN bags can be (optionally) purchased with a removable internal frame with aluminum stay:
Synapse 19
Synapse 25
(See also: the Synapse 19 or Synapse 25 Internal Frame page, where those frames can be purchased separately.)

So, do you need an internal frame for your backpack?

Our goal is to provide options in order to do our best to include everyone and help them carry a bag comfortably. In the end of course, it's your call. We'd recommend considering the information we've outlined above and using your own discernment: figure out what's best for you as opposed to whatever might be the current dogma in the world of outdoor gear. That might be carrying the heavier, classic external frame pack you’ve always loved, or going totally frameless and minimalist. You might mix it up depending on the load, the season, or length of trip. The Synapse’s internal frames are pretty easy to install and remove, so you may find yourself adding the frame for a long hike and removing it for a short weekend getaway.

We've made an effort to offer internal frames that provide all of the benefits without requiring a firm commitment: it's totally optional whether you use one of our included or add-on internal frames. A bunch of us here at TOM BIHN are avid hikers and sometimes backpackers, and we choose to carry frame or frameless packs depending on where we're going and what we're carrying.

Perhaps the most important thing of all: going out into the world. The gear we take with us is continually evolving; our experience dictates what we carry.