Earlier today I filmed the product video for the new Sierra Designs Flex Capacitor 40-60 Pack, which with the High Route Tent 1FL currently constitutes SD’s “Skurka Series.” To develop my script, I had to prioritize and succinctly describe the pack’s must-mention specs and features. Later I’ll write a self-critique, as I did for the High Route, but for now I want to explain what makes the Flex Capacitor stand out.
1. It’s just $200 and 2.5 pounds (1.1 kg)
The Flex Capacitor is built well and has the right feature set. But we held down its price and weight by keeping its design simple, using reasonably priced materials, and pushing hard on our partner factory.
2. Volume adjustment
Using the adjustable gusset on its front side, the Flex Capacitor’s volume can be adjusted between 40 and 60 liters (2440 to 3660 cubic inches), which is the difference of nearly two BV500 bear canisters. Load-carrying performance is excellent throughout this range, essentially making the Flex Capacitor a “two packs in one” proposition. The gusset is a more functional solution to volume adjustment than conventional extension collars and cinch hooks.
3. Full suspension
Last year I carried out an elk from the Colorado Rockies with a Flex Capacitor prototype. The first load, which weighed 69 pounds (31 kg), was crushing. But the Flex Capacitor carried it shockingly well, and I used it again for the second 60-lb load, despite having a true meat-hauling pack in the car. The Flex Capacitor features a stiff Y-shaped tubular stay made by DAC; it anchors directly into the hipbelt for efficient load transfer.
4. Back panel airflow
Designers face a mutually exclusive choice with pack panels: load-carrying or user comfort. Packs carry best when they are flush against the back, because the load is closest to the user’s natural center of gravity. But gappage between the pack and user helps to avoid SBS, or “sweaty back syndrome.” We chose user comfort, but did so without adding much weight (see #1) or giving up much load-carrying performance (see #3).
5. Six external pockets, including a shoulder strap pocket
Hipbelt pockets and side pockets should be standard on any backpacking pack. The Flex Capacitor has them, and they’re very functional. We installed a fifth pocket in the top lid, for small essentials. My favorite, however, is the shoulder strap pocket, which is sized for a 20-oz water bottle or bear spray.
6. Easy in/out top lid
Like me, do you find annoying the multiple buckles, straps, cinch cords, and lids that you must futz with in order to access your pack’s main compartment, or to close it up? How does a top lid with a single, big-toothed, easy-gliding zipper sound? Yeah, it’s awesome.
7. Compression and utility
The expanding gusset could serve double-duty as a compression system, but we added two removable horizontal straps anyway. First, they decouple volume adjustment from load compression. Second, they are useful in securing trekking poles, ice axes, shovels, or even skis (no metal edges, please).
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