Weight

A lighter pack will sometimes carry a little better than a heavier pack, but lightweight might come at the expense of durability. Usually, pack weight indicates carrying capacity and the amount of beef (or lack of) in the suspension and padding.

Volume

Consider what you might carry and don’t undersize your pack. You’ll need around 2,500 to 3,000 cubic inches for your rack, rope, lunch, water and cold weather gear. Figure 3,500 to 4,000 cubic inches if you add bivy gear, and 5,000 plus for multi-day trips into the mountains.

Extension

With some top-loading packs you can get extra space by rolling out, unzipping or un-tucking the sleeve extender. See that your pack lid has straps long enough to secure the lid even when the extension cuff is fully loaded. In a dire situation you can stick your legs in the empty pack and pull the sleeve up around your waist as an emergency half bivy bag.

Women’s Fit

Some companies make packs designed specifically for women. These packs can feature closer shoulder straps, narrower waist belts and so on. The key is getting the best fit possible regardless of how the pack is marketed.

Frame Type

A crag pack will often have a frame made of a closed cell foam pad. For short approaches with relatively light loads that’s all you need. Larger packs, designed for longer approaches, will have beefier frames made of plastic sheets or metal stays to distribute the load and absorb shock. Again, fit is paramount and individual. The load should ride close to the body with minimal sway if you intend to climb in the pack. Often, packs with plastic frames will hug the body. For an approach pack, internal metal stays provide more support.

Top Load

Top-load packs are more weatherproof than panel-load packs. They are easier to handle and less likely to spill in high-angle situations, such as when they are clipped to a belay. Most alpine and ice packs are top loading.

Panel Load

These packs offer multiple access points, which make it easier to see and access items in the middle or at the bottom of the pack. Many crag packs are panel loaders.

Number of External Pockets

Keep it simple. A crampon carrier can be nice, but avoid packs with copious external pockets. They snag and complicate packing.

Crampon Carrier

A nice addition to an alpine pack. Especially useful are the crampon pockets, which let you stuff in crampons, rather than strap them onto the pack.

Tool Carrier

Two ice axe loops are mandatory for any alpine pack. Before you buy a pack, check that your tools fit in the tool loops—many don’t.

Daisy Chains

Internal and external daisy chains help with gear organization. You can use external daisy chains to organize the rack and as easy clip-in points for water bottles, stuff sacks and other items at bivies or belays.

Hydration System

These can be useful, but are prone to freezing and puncturing.

USE

Cragging

2,500 to 3,000 cubic-inch packs that panel load are the most adept for cragging. Crag packs with sturdy haul loops are especially useful.

Alpine

3,000 cubic inches for an alpine day pack. 3,500 cubic inches if you add bivy gear. Get a pack that has two tool carriers, crampon straps or a crampon carrier and a haul loop. For alpine packs, see that you can operate all the zippers and closures while wearing gloves.

Mountaineering

3,500- to 5,000-cubic inch packs are the ticket for multi-day trips into the mountains. Insist on two tool loops, a crampon carrier and an extension sleeve. Fit a mountaineering pack most carefully of all: a poorly fitting pack will magnify the 50+ pound load you’ll carry.