Whether you are borrowing a pack from FOP or bringing your own, it is important to understand how they work. We have compiled the following information so that you can educate yourself on what to look for when buying or renting a backpack. A poorly fitting pack can be very uncomfortable. In addition, a properly fitting backpack is safer, because it will allow you to be more balanced and therefore more agile. So take the time to read this page - it is packed with useful information.

Internal vs. External Frames

Either an internal frame pack or an external frame pack will get you to your destination, and FOP rents both. Internal and external frames fit people differently. Often people find they prefer one over the other, so be sure to try on both types of packs and weigh the advantages and disadvantages of each. In the end, however, comfort is the most important aspect of pack selection. Make sure you are comfortable carrying your pack with weight in it.

Internal Frame Pack

An internal frame pack has a rigid support frame sheet with "stays" (2 rigid rods sometimes made of aluminum) that line the inside of the pack. You cannot see the frame or stays from the outside of the pack.

Internal frame packs come in many shapes, sizes, and levels of quality providing a tremendous variety of weight-bearing options. In general, because they lack an external frame, they keep the load weight closer to the back, which makes the pack more stable in general and allows a backpacker to have more agility on difficult terrain. Internal frames are also usually sleeker, which helps on narrow trails. Many internal frame packs are also lighter because of their small frames.

Internal frame packs may be more expensive, so shop around if you decide on an internal frame pack. Because they hug the body so closely, if you decide on an internal frame pack, it is important to get a pack that is sized to fit you.

External Frame Pack

An external frame pack has a frame attached directly to the outside of the pack. External frame packs have several features that distinguish them from internal frame packs aside from the frame location. In general, they are easier to fit to your body because they can be easily adjusted at the hip belt and waist belt. This means if you are borrowing a pack from a friend, an external frame will be easier to adjust it to fit your body. External frames also carry the weight of your pack higher, allowing for a more upright stance while walking. The frame in these backpacks holds the pack away from your back, allowing air circulation through the back. In hot weather and while hiking, this circulation can be a welcome relief. External frame packs are slightly more cumbersome than internal frames due to the width of the external frame and the pack weight being held farther away from the body. Finally, in general, external frame packs are less expensive than equivalent internal frame packs.

Fitting a Backpack

When borrowing a pack from FOP or a friend, or shopping for a pack, it's important to know how to adjust the pack to provide the best weight distribution. This will allow you to experience how the pack should feel on the trail.

When adjusting the straps on your pack, you are ideally looking to feel about 3/4 of the weight of the pack on your hips, and 1/4 or less of the weight on your shoulders. Your hips are made to support more weight, and having the weight centered around your hips will allow you more agility and control while backpacking. If you find yourself leaning forward too much while backpacking, it may be because you are compensating for too much weight pulling back on your shoulders.

To achieve this weight distribution, the first strap to clip together and adjust is the hip belt. The hip belt should sit directly over or slightly above the ends of your hip bone on the front of your body. Tighten this strap fully so you feel no weight on your shoulders. The next strap to adjust is your shoulder straps. Tighten these until the straps are snug against your shoulders, but do not over-tighten so that they take weight away from your hip belt. Many internal frame packs have other straps such as a sternum clip to hold the shoulder harnesses together and load adjustor straps that extend from the top of the pack down to the shoulder harness. Once the shoulder and hip straps are adjusted, these other straps can be adjusted.

When you take the pack off, follow the adjusting process in reverse to loosen the straps before you take the pack off. This adjusting process should be done every time you try the pack on. This will allow you to find the optimal fit each time you put the pack on. Also, while hiking, the pack may loosen slightly, so continue to adjust over the course of the day.

Sizing a Backpack

Pack sizing is an involved process. Because it will be the means of transporting all your heavy gear, it is important to find one that will fit you properly. Here are aspects of packs you need to consider when choosing and sizing a backpack:

  • Frame size: Frame sizes are measured according to torso length (about the length from shoulder to hips). To find your torso length, use a measuring tape to measure from your C-7 vertebra (the big one at the base of your neck) to a point on your spine level with the tops of your hips. Most packs are made for specific torso lengths, so finding this measurement will help in pack selection. Some packs have adjustable torso lengths.
  • Hip belt: Once tightened, the lateral midline of the hip belt should sit directly over your hipbones. Too low or too high hip belts may necessitate finding a different torso length pack or adjusting the torso length of the pack. The padded part of the hip belt should wrap around approximately 2 1/2" past your hip bone. There should be enough adjustment in the straps to accommodate weight loss and/or added clothing. Be cognizant of what you wear underneath a hip belt: a belt or a bulky and "ruffly" elastic band waist can cause chafing and discomfort. Different packs can have hip belts with varying degrees of padding.
  • Shoulder straps: Shoulder straps should wrap around your shoulder completely in the back, staying flush with your back until the point where they attach to the pack. The load-adjustor straps that are above the shoulder straps should be at a 25-40 degree angle and should always be snug. If the shoulder straps extend too far down the back, or extend straight back from the shoulder(not hugging the shoulder), adjust the torso length until they hug the shoulder completely to the back of the shoulder. Shoulder straps should be ergonomically contoured (tapered and curved) to fit nicely over the top of your shoulder in front, and then under your arm. Like hip belts, different packs have shoulder straps with varying degrees of padding.
  • Shoulder stabilizer straps (a.k.a: load lifters, top tension straps, or load balancers): These pull the load in over your shoulders to increase stability and lift the shoulder straps off of nerves around the collar bone. They help vary pressure points and improve the comfort and fit of your pack.
  • Capacity: Check the capacity of the pack you are trying on and compare it to what FOP recommends. It is always better to get a bigger pack and not fill it than it is to stuff a small pack full of gear. In the same regard, an enormous pack that is not used will just be extra weight to carry.
  • Comfort and weight distribution: Once you have the pack adjusted, ask the salesperson to add weight to the pack (at least 20-30 lbs.) to feel how the pack feels when loaded full. This is the true test of how comfortable a pack will be. Also, walk around the store to see how the weight moves with you. Walk up stairs if possible, jump, run, or just turn your body from side to side to see how the weight responds to different movements.

Pack Features

Women-Specific Packs

For many years packs were made without much thought to gender. Today, companies such as Gregory, The North Face, Osprey, Lowe Alpine, and Kelty all have packs that are specifically designed for women. Why? Women generally have narrower shoulders, shorter torsos, and wider hips, and a pack that has been designed for someone with broad shoulders, narrow hips, and a long torso is simply not compatible with their "frame". It is worth trying a specialty bag on for size!

Sternum Straps

These straps pull the shoulder straps in toward the center of your chest directly over your sternum. They help vary pressure points and also increase comfort.

Pads and Padding

In addition to hip belt and shoulder-strap padding, padding along the back of the pack can improve comfort. The padding on the back of your pack should protect your back / shoulder blades. Over-padding is not necessary; even though it looks more comfortable it can get in the way. Too much padding may also cut down on air flow.


Consider if the material is light or heavy and if it will stand up to abrasion/abuse.


Extra pockets can be useful for storing things on the outside of a pack for easy access. Some packs have lots of compartments others do not. Some packs have a single divider on the inside of the pack that divides the pack in two. This can help organize your gear on the inside (ie: keep food items away from gear, etc) Some bags even have an internal pouch for a water bladder and a hole for a hose (like a CamelBak) so that you can drink while you hike.

Separate Sleeping Bag Compartment

Many packs have a separate sleeping bag compartment to keep your sleeping bag accessible even while it is at the bottom of your pack.

Lids and Buckles

Some pack lids (the very top of the pack) are multi functional and turn into a hip pack for small hikes. Others really fit to the bag snugly while some "float" on top. Look for buckles that are fast and easy to clip and unclip. The fewer there are on the bag, the simpler a time you will have!

Compression Straps

These straps on the sides and bottoms of many bags help consolidate the load and bring it closer to your back which helps improve balance.

Rain Cover

If all your gear is packed in Ziploc Bags or trash bags then you might not need one. They are an extra feature that is not necessary.

Top-loaders vs. Panel loaders

Most packs are top-loaders, meaning you load all the gear in from the top of the pack. Top loaders usually close through a system of cinch cords. Panel loaders have a large panel that zips shut, allowing easy access to interior gear. However, they do take care in packing, because you cannot overstuff them because of risk bursting the zipper. Some packs will combine both types of loading system into one pack by having a zipper and a top loading area.

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