It is obscenely huge. It fastens shut and watertight with a roll-top closure. A backpack harness system lets you strap it on and hike, ferrying immense loads through airports and down backwoods portage trails alike.
The SealLine Pro Packs are essentially giant vinyl duffel bags. They open wide to reveal a capacious hold that can swallow about 7,000 cubic inches worth of gear.
I have used a SealLine Pro Pack on a half-dozen trips this year, including for international travel as well as on a raft excursion where the pack was tied to the deck. At $169.95, the handy and bombproof bag -- mine's been dubbed "Big Yellow" -- has proven its worth a few times over.
The Pro Pack is 100 percent waterproof for terrestrial use. Rain, sleet, snow, or dripping cargo holds are no match for the thick vinyl fabric and roll-down top.
If you plan to use it whitewater rafting, Pro Pack manufacturer Cascade Designs (www.cascadedesigns.com) says it will withstand quick submersions and will float if dropped in the water.
The pack has a reinforced vinyl bathtub-style bottom and tough vinyl sides. Webbing straps cinch to tighten down the top. Durable buckles snap it shut.
The pack's adjustable suspension system is supportive for big loads. There's a padded hip belt and a grab handle to lift the sack off the ground. For snag-free transport, the backpack harness and belts can be removed.
I loaded the Pro Pack with 50 pounds or more on numerous occasions. The pack straps and belt are adequate for huge loads, though the rigid panel under your back can bow out from the pack body with extreme weight.
The pack comes in four colors and weighs about six pounds when empty. It stands about 30 inches tall.
As a bonus, the pack is made in the USA in a Seattle factory.
Overall, "Big Yellow" has been a solid product after much abuse this year. It totes huge loads. It keeps my gear dry. It does exactly what it was designed to do.
--Stephen Regenold is founder and editor of www.gearjunkie.com.