Osprey Atmos 65 Pack

• Material: 210D double ripstop Cordura nylon, 210D broken twill high-tenacity Cordura nylon, stretch woven nylon with Lycra
• Volume: [S] 3800cu in (62L); [M] 4000cu in (65L); [L] 4200cu in (68L)
• Suspension: 10mm aluminum frame, twin titanium struts, thermo-formed harness & hip-belt, ventilated back panel
• Hydration Compatible: Yes
• Torso Adjustment: Yes
• Detachable Pack: No
• Sleeping Bag Compartment: Yes
• Rain Cover: No
• Access Types: Top, left front zip pocket
• Pockets: [External] 1 lid, 2 front, 2 side, 2 hip; [Internal] 1 lid
• Snowboard Carry: No
• Ski Carry: No
• Gear Loops: 2
• Ice Axe Loops: No
• Shovel Pocket: No
• Weight: [S] 3lb 6oz (1530g) [M] 3lb 9oz (1630g); [L] 3lb 8oz (1570g)
• Recommended Use: Overnight, weekend backpacking
• Manufacturer Warranty: Lifetime

The pack also includes a sewn-in hydration sleeve with a well-marked exit port, ensuring that you stay well hydrated on the trail. And serious trekkers will love the Stow-on-the-Go trekking pole attachment, which leaves both your hands free for climbing. Other details include a zippered sleeping bag compartment with a removable divider, dual ice tool loops and bungee tool tie-offs, and a couple of dual mesh side pockets with InsideOut compression, which allow you to tension and secure your load easily when the pockets are in use. The pack--which is available in graphite grey, green apple, and aspen gold colors--comes in small, medium, and large sizes.

The Atmos 65 includes a pair of vertical zippered front pockets and a trekking pole attachment.

• Dimensions: 14 x 30 x 12 inches (W x H x D)
• Small: 3,800 cubic inches; 3 pounds 7 ounces
• Medium: 4,000 cubic inches; 3 pounds 9 ounces
• Large: 4,200 cubic inches; 3 pounds 12 ounces

Amazon.com Backpack Guide
Finding the Right Backpack
For extended trips into the backcountry, there's no getting around the fact that you'll have to carry life-sustaining supplies on your back. Here are some things to keep in mind when shopping for a backpack:

Internal vs. External
Up until late 1970's, external frame packs--which consist of an exposed, lightweight metal frame attached to a fabric pack-bag--were the only thing going. In recent years, though, packs that place the support structure of the pack inside the pack, known as internal frame packs, have boomed in popularity.

The good news about internal frame packs is that they hold the weight of your load close to your body, making it easier to maintain your balance on uneven terrain. Meanwhile, internals provide stiffness and support, but they are not completely rigid, which makes them more flexible when you're doing active sports. With the added flexibility comes a high degree of compressibility, meaning you can use the pack's compression straps to cinch down your load and keep items from shifting and throwing you off balance. Internals also sport slimmer shapes that allow for more arm movement in all directions--another big plus for off-trail bushwhackers, skiers and climbers. Last but not least, internal frame packs offer a greater range of adjustability in the shoulder harness and hip-belt than external frame packs.

There are some negatives for internals. First, once packed, it can be difficult to grab needed items out of them quickly. And because internal frame packs consolidate the load into a single, body-hugging unit, proper packing is very important. To distribute the weight properly, you should pack your heaviest items close to your back and in the middle portion of the pack-bag. Plan on getting a sweaty back with an internal, too, given the fact that they are pressed right against you. Finally, internal frame packs are priced higher than external models.

External frame packs are very good at focusing the weight of a load directly to the right place: your load-loving hips. While internals, when properly packed, do this effectively, too, you can always rest assured that an external will distribute the load evenly, no matter how unevenly packed it may be. Externals also offer easy access to your gear via multiple, easily-accessible compartments. Plus, because externals don't situate the load directly against your back, you'll enjoy far more air flow. Finally, if you're on a budget, or you're buying for a growing child, externals are more affordable.

If you plan on hiking on easy to moderate trails and you don't need a lot of body movement, you'll probably be fine with an external. But because externals are so rigid and inflexible, challenging trails or any kind of off-trail pursuit can become painful and frustrating. Also know that your balance is far more compromised with an external frame pack during activities like stream crossings and hops through talus fields.

Packs for Shorter Trips
In addition to backpacks designed for overnight trips, rucksacks are great for day-trips, warm-weather one-nighters, single-day ski trips, or fast alpine assaults. Some rucksacks blur the line between backpack and rucksack with integrated internal supports and sophisticated hip belts and shoulder harnesses. Choose a pack in this category based on your intended use. Short day hikers don't need an internal frame, while climbers and skiers with heavier loads likely do.

Sizes and Capacities
Packs in the 3,000 cubic inches and lower category are good for day hikes or overnighters in warm weather with minimal gear. Packs in the 3,000 to 4,000 cubic inch range are good for one- or two-night trips in colder weather. If you're going to be out for up to three days, look for a pack in the sub-4,000 cubic inch range. Choose a pack with 5,000-6,000 cubic inches for week-long outings. And finally, for trips lasting a week or more, you'll need something in the 6,000-plus cubic inch category. Keep in mind, though, that bigger packs weigh more, and since every ounce counts, you'll want to choose a pack that offers just enough space for your outings and no more.