As third-party reviews and commentary about the Sierra Designs Flex Capacitor 40-60 Pack gets posted, I’ll be compiling them here.
User reviews at SierraDesigns.com
For reviews from “regular” users, go here.
We tested it, and not only does the pack expand and contract to maximize uses, but it also carries extremely well. The 2-lb. 9-oz. pack can tote between 40 and 60 liters. At $200, it’s a one-quiver kind of pack many people can use across all their backwoods adventures.
Overall, [the Flex Capacitor] is a sweet-carrying, versatile backpack. [It] stands out thanks to a clever expanding design that lets it carry between 40 and 60 liters while still acting “full.” The pack expands outwards, not up and down, by tightening or loosening a series of compression straps. This gives the pack more versatility for those who want a single pack to do a lot of jobs. Even though my pack was carried fairly empty, it didn’t shift on my back and I had tons of room to expand if I needed more gear or food for longer excursions.
Overall, this is a well designed, functional, light backpack that can carry significant weight if needed. It will provide a versatile solution for hikers and others who want a backpack for many uses on high mountains and trails anywhere you may roam.
Paul Magnanti (PMags.com)
I think this pack will work well for the person who needs a quiver-of-one for prime three-season use and even into deep shoulder season. At $199 it is a reasonably priced pack and does not weigh that much especially when compared to [similarly featured models].
More minimalist solo backpackers can probably get away with a sturdy, but still pretty light, [frameless pack] for a variety of needs.
But if your base weight is a little higher, need a more versatile pack with better weight hauling capability, prefer more support/comfort and need more storage capacity, a different pack is preferable. The Sierra Designs Flex Capacitor could easily fit this set of needs.