The Arc'teryx Index 40 Bouldering Bag packs serious organization into a carry-on-friendly footprint, with dual 20L zippered compartments that let you sort climbing gear without everything turning into a tangled mess that requires archaeological excavation. Mesh dividers keep things visible while letting damp gear actually dry instead of festering in darkness, and that external zipper on one compartment means you're grabbing your shoes or chalk without unpacking everything.