Which backpack will survive ten days in the Amazon?

A: It's a little hard to say exactly what he needs in a pack because I'm not clear on how much stuff he's expected to carry. But I'll assume he needs to lug some personal gear, but not a tent, cookset, that sort of thing. If so, then a pack in the 3,000- to 4,000-cubic-inch range would suffice. In the Kelty line, the Moraine ($130; www.kelty.com) offers a good range of versatility, with 3,300 cubic inches of capacity, a decent suspension, and lots of loops on the outside for lashing extra gear. I also like Gregory's Z Pack ($179; www.gregorypacks.com), which is similar in size to the Kelty but promises a little better suspension for heavier loads.

Neither of these is technically a hydration pack, but it's easy to retrofit either one with a CamelBak StoAway ($35; www.camelbak.com), which is designed to slip into most any pack and provide the carrier with 70 ounces of liquid. Both the above Gregory and Kelty packs are equipped with hydration bladder sleeves and "feed" tube openings in the straps.

I can't imagine that a warm sleeping bag is in order. REI's Travel Sack +55 ($59; www.rei.com) should be just fine—a light synthetic bag with just enough insulation to keep you from getting chilled in warmer climates. A Cocoon Silk Mummy Liner ($49) offers a little extra warmth if it's needed, serves as a standalone blanket on very warm nights, and keeps the bag cleaner when used with a sleeping bag.

Hope that helps keep your guy on the go and comfortable as he's communing with the wonderful critters and plants of the Amazon!

For more expert reviews of a range of haulers, check out Outside Online's Backpacks Buying Guide.