Fully loaded, it can tip the scales at 80 pounds and look like an overgrown first-grader - three feet high and about as wide, with fleshy appendages jutting here and there.
Now, the air assault infantrymen from the 101st Airborne Division are discovering how well they packed their supplies, from foot powder to mean-looking pointed bullets. These soldiers, part of the 3rd Battalion of the 327th Infantry Regiment, are deployed in Iraq, near Najaf, relying on their packs.
Back in Kuwait, at Camp Pennsylvania, Spc. Anthony Wright of Essex, a tall, thoughtful 20-year-old who joined the Army out of Eastern Technical High School in 2000, was ready days before moving out. Both of his packs and his ammunition-carrying body armor vest bulged with three weeks of supplies.
The rucksack is the biggest piece of the package and comes with a long packing list spelled out in minute detail by battalion leaders. The list runs to 29 items, and only one - underwear - is considered optional. For the most part, Wright stuck to the program but did give himself more generous portions.
His bag's main compartment has exactly seven pairs of socks (the list calls for five), eight T-shirts (the list says just one), 10 empty sandbags, six meals-ready-to-eat and two sets of desert camouflage uniforms. It also has black gloves, rope cord, sewing kit, towel and toilet paper. But no underwear.
If Wright goes into combat, he will do so without undershorts. In that setting, he says, they cause chafing and other problems not conducive to fighting.
Below the main bag is a second, smaller pouch. It is taken up completely by a protective chemical suit and a green sleeping bag.
Wedged between the two compartments is an E-tool (for entrenching), a versatile shovel that folds into three pieces.
In a pouch protruding from the ruck's left side sit 30 disposable razors and a can of shaving cream, as well as a camouflage rain poncho. In the right pouch there is a waterproof rain suit, top and bottom.
On back of the ruck is the claymore pouch, meant to hold claymore antipersonnel mines. Wright used that precious space for extra gloves, black winter cap and goggles.
Also fastened to the outside is a pair of two-quart canteens, with at least another quart to be stashed in the gear. Beyond that, he was leaving camp with a Camelback drinking system on his back, giving him another three liters until more water supplies arrive.
Tucked between the ruck and plastic frame is an IV bag with saline solution. Every soldier carries one in case a buddy is overcome with dehydration.
It is not for nothing that the rucksack is called the sustainment load. It will be three weeks at least before soldiers' "A" bags show up with more of their belongings.
The assault pack, by contrast, is much smaller. While the ruck is worn only until arriving at a base camp or bivouac site, the assault pack is, as its name suggests, worn into combat.
Think of it as the soldier's overnight bag, only much heavier. It resembles a high school student's backpack, with the same woodland camouflage pattern as the ruck.
The main pouch is taken up by Wright's primary chemical suit, the one he would don first in the event of an attack. The suit comes with boots, gloves, showercap-like helmet cover, pants and a shirt with hood that pulls up over the gas mask.
Under the main pouch is a pack to keep his "polypro," a high-collared, brown sweat shirt made of polypropylene to pull sweat away from his body. It is a way to keep warm on cool desert nights. He also has a spare brown T-shirt of the sort worn by most soldiers.