Going backpacking? Well, there are about a trillion guides for which widget will make an imperceptible improvement to your hike. You may not need a tri-folding pour over kit, but were certain you’ll need a backpack. Choosing the right backpack can make or break your vacation, your honeymoon, or your thru-hike. Here’s an expert’s advice designed to make the choice simple. Oh, and well teach you the best way to pack it, too.

　　Which Backpack Style Is Right For You? Pretty much all backpacks employ internal frames these days. Even the fancy ultralight Dyneema packs that are all the rage these days use a few aluminum stays that can be considered a frame. Stick with an internal-frame backpack unless you’re an experienced hiker with a specific requirement that necessitates a burlier external frame.

　　But there are infinite options for internal frame backpacks out there. One big differentiating factor is how the pack rests against your body.

　　Cheaper options (or speciality ones designed either to support immense weights or to be used in cold conditions) will use foam back pads that sit flush against your body.

　　Mesh suspension, which is tensioned between the frame stays, conforms to your body and provides an air gap between you and the pack. Mesh suspension is a more broadly comfortable design that works well across different body shapes, and will keep you cool on the trail.

　　The tensioned mesh on this Osprey holds the pack body off your back, adding comfort and cooling. But the hip belt on this Exos Pro 55 is also a good example of a less-than-robust design which wont be comfortable supporting weights in excess of 20 pounds. (Photo: Osprey) Which Size Backpack Should You Buy? For anything beyond a day hike, most backpackers will want a pack between 45 and 65 liters in capacity. If you have a smaller body, choosing a smaller capacity will increase comfort, decrease weight, and, since your clothing and sleep system are probably smaller too, should correspond to the size of your stuff. The opposite is true if you’re larger.

　　If you’re planning a trip in adverse weather conditions, one that’s more than three nights long, or you have gear to carry to support additional activities, you’ll want a pack at the larger end of that range so you can fit all your stuff.

　　Sizes larger than 65 liters exist to support speciality uses like mountaineering or hunting, which then also dictate their own designs and materials that may compromise comfort on the trail and typically add cost. Unless you need a bag specifically to haul ropes or quarters, try and avoid buying a pack larger than 65 liters.

　　Which Backpack Features Should You Look For? It’s the frame’s job to support the weight carried in the pack and transfer it down into the hip belt, where it can be supported by the largest muscle group in your body—your legs. So, beyond suspension and capacity, the single most important aspect of a pack is hip belt design.

　　In order to support that weight, a hip belt must be rigid when it’s secured to your body. Belts that flex and twist will do so when loaded, creating pressure points and chafing as you walk. Look for belts that can’t be twisted or otherwise deformed when fastened, and which feel comfortable on your unique body.

　　Beyond fit, packs may offer all manner of straps, pockets, zippers, clips and fabrics. Because all of that adds weight and potential points of failure, the best packs are often the simplest ones. Look for a fabric that’s robust enough to hold together and shed some precipitation, but avoid anything that’s actually waterproof, overbuilt, or over-featured.

　　If a pack comes with a removable summit pack/lid, excess webbing to attach bulky objects, or other non-mission-critical features, consider removing or cutting them off once you’re sure you don’t need to return it.

　　Also think about how you want to carry your water. Bladders help locate water’s weight close to your body, inside the pack. Bottles are easier to access. The former requires a sleeve and the latter specialty pockets (or a willingness to get in and out of your pack).