From Gear Patrol:

“When it comes to making tough backpacks, GORUCK is no slouch — it’s GR1 backpack is our favorite military-inspired daypack available — and its latest bag, the GR3, brings that same aptitude to the carry-on category. At 45 liters, the GR3 is the biggest rucksack in GORUCK’s stable and the ideal size for travel.”

Read more here.