Backpacks have come a long way... They’ve got all sorts of extra convenient features now, like hipbelts, organizers and hydration sleeves, and there seems to be a special pocket for just about everything! So it can probably be a little overwhelming when trying to find the pack that’s right for you. How do you even begin to know what to look for?

Ultimately, you’ll need to figure out whether you need an internal or external frame pack. But in order to answer that, you first need to determine what you’re going to be using the pack for. While both internal and external frame packs basically serve the same function, each is designed for a different set of activities. Keep reading to find out which is right for you.

Internal frame packs are mostly used for climbing, hiking and skiing. They were actually developed by rock climbers who wanted a narrow pack that wouldn’t interfere with arm movement while they were climbing. At the same time, they wanted the pack to hug their backs for a secure fit. And that’s how the internal frame pack was born! It follows your body contour more closely, and the pack moves with you instead of pulling you to one side or another. If you’re rock climbing, this is especially important because you can’t afford to be pulled in a certain direction unexpectedly.

As far as the specifics go, internal frame packs are the taller, narrower-looking packs. They’ve got fewer outside pockets than the external frame packs in order to prevent the pack from getting caught on something while you’re wearing it.

There are advantages and disadvantages of internal frame packs. It’s easier to keep your balance and stability when wearing an internal frame pack since it hugs your body. Internal frame packs are also pretty flexible, so they move with you.

On the flip side, as previously mentioned, there aren’t many external pockets, so most of your gear has to go into the main compartment. Internal frame packs can also be hot to wear. Since the pack fits so closely, it’s difficult for air to flow along your back, so you’ll sweat more while wearing it.

External frame packs are great for trail hikers and beginner backpackers. They came along before the newer internal frame packs existed. External frame packs have an external, tubular-aluminum frame that supports the pack. Over the years, these packs have really improved both in the materials used and the overall construction. Today, they’re significantly lighter and stabler than before. They’re actually lighter than most internal frame packs, sometimes even two to three pounds lighter.

External frame packs fit differently than internal frame packs, so you don’t get as hot when you wear them. They don’t fit as closely to the body. With the pack positioned slightly off the back, air can pass through, keeping you cooler. The frame also allows most of the weight to be carried on your hips instead of your shoulders.

Like the internal frame pack, the external frame pack has its advantages and disadvantages. One good thing is that they’re much cooler to carry because of their fit. And because of the extra outer pockets, there are more compartments to choose from when storing your gear. You don’t have to worry about your load sagging, either, because of the heavy-duty external frame.

The main disadvantage of external frame packs is that you can’t move as easily while wearing one. The external frame doesn’t allow much ease of movement, so it can be downright cumbersome if you try to climb while wearing it. That’s why these packs are recommended mainly for backpacking and trail hiking.

Now that you know the differences, it’s time to choose your pack. There are lots of factors to consider when choosing your pack, but perhaps the most important thing to think about is how long your trip is going to be. The length of time you’re going to be traveling and the amount of space you need go hand in hand. JanSport classifies their packs as Half Day, All Day, 1 ½ Day, Weekender, Weeklong and Week Plus. The following chart should help you decide which pack is right for your next adventure: