As over-engineered as it gets, to take you to hell and back Cockroaches, Twinkies, and GORUCK would be all that's left were the world to end. Over-engineered to mythic proportions is why we like it, and why the brand is synonymous with the most durable bags on the market for everything from day-to-day city life to whatever the modern world can come up with.The 21L and 26L GR1 and the 26L and 34L GR2 all share the same best-in-class features for years of urban and rugged adventures, and they're all TSA-compliant as a carry-on. The right ruck for you depends on what you're looking to use it for. The 21L is ideal for single-day treks and your minimalist packer whereas the 26L and 34L are desirable for longer excursions and rucks (i.e. bring on the painfest) where an added 5 liters or more of storage capacity is needed. No matter which bag you choose, the GR1 and GR2 Heritage bags are overbuilt to last a lifetime. 10.10 oz. Army Duck Wax Canvas construction (with a rainproof Martexin wax finish), a water-resistant 210D black cordura back panel, and silent YKK zippers ensure their longevity. But these bad boys aren’t just for the backwoods, their sleek appearance, secure laptop compartment, and TSA-friendly dimensions enable them to perform just as well on the grid.