The early fanny pack was a generic nylon sack that invariably rode your ass like your eighth-grade gym teacher. But the beast has evolved into two species: One descendant is a genetic dead end—that little neon-green pocketbook you still see jiggling on rear ends at the mall. Its more serious cousin formed a family of highly specialized lumbar packs that, thanks to internal frames, compression straps, and wide waist belts, carry a variety of loads tight to the small of your back. They've become so specialized that you might want to own more than one. Keep the fishing pack stocked by the door for the evening rise, and store the hiking pack in your car. From a minimalist hydration system for trail runners to a huge pack ideal for an overnight on the Continental Divide mountain bike trail, here's the best of the breed.

TRAIL RUNNING
The CamelBak FlashFlo ($40; 800-767-8725, http://www.camelbak.com) has 136 cubic inches of storage—enough for a few energy bars, a bag of gorp, and 45 ounces of water to wash it all down. Snug up the compression straps on each side of the pack to keep your keys from jingling when you're out jumping streams. Two clips secure the water tube to the mesh waist belt so you can unclip it and take a swig on the fly. Unfortunately, if you overheat on the trail there's nowhere to stash the layer you'll want to shed. Shock cords crossed in an X could solve this problem without really adding weight.

ADVENTURE PHOTOGRAPHY
The Lowepro Orion Mini ($50; 800-800-5693, http://www.lowepro.com) is big enough at 240 cubic inches for one SLR camera, a few rolls of film, a spare lens, flash, battery, and lens cloth—perfect for amateur photographers who want to haul their equipment without the aid of a Sherpa. The lid opens away from your body to reveal padded dividers that float the camera lens down, so you can easily draw-and-shoot while skiing or mountain-biking. Better yet, removing the dividers instantly transforms the Mini into a portable beer cooler, though that's not in the manufacturer's instruction booklet.

FLY-FISHING
Chest packs carry more tackle and let you wade deeper, but if you bike or hike to your secret lunker pool, the 240-cubic-inch Flats Plus Fanny Pack by JW Outfitters ($89; 760-471-2171, http://www.streamworks.org) will do nicely. Two insulated, 16-ounce water-bottle holders sandwich a hinged storage compartment. Undo a strap and the compartment rocks forward to reveal a hidden work.station with a mesh panel to accommodate four spools of line—plus three elasticized pockets for forceps and clippers, two tiny bungee cords to keep them from getting dropped, and enough leftover room for two fly boxes and a lunch.

MOUNTAIN-BIKING
If you've had that "I'm going over the bars" feeling while biking downhill with a big daypack, you'll understand why True North developed the Load Monster ($89; 800-873-5725, http://www.trunorth.net). It carries backpack-scale weight at the small of your back—low enough to keep your mount under control. Long shoulder straps relieve you from having to cinch the waistbelt until you faint. At 1,340 cubic inches, the Load Monster is ideal for fair-weather bivy-sack camping, an overnight in a shelter, or, if you live in Alaska, any time you leave the house.

DAY HIKING
With two fiberglass struts and six compression straps built around a plastic frame, the 630-cubic-inch Q10 by Arc'Teryx ($89; 800-985-6681, http://www.arcteryx.com) has better suspension than most daypacks. Add features like a water.tight zipper, two one-liter water-bottle holders, and a rugged exterior pouch roomy enough for a mountain parka, and you have a lumbar pack worthy of lightweight summertime assaults in the Adirondacks or the San Juans. And unlikemost waist belts, the Q10's can be adjusted so that the padding wraps com.fortably around your hips, no matter what your size. —MARC PERUZZI

Photos: Clay Ellis