The lightest framed pack is a Zpacks. Again.

The lightest internal-frame backpack you can buy today is the Zpacks Arc Haul Ultra, and it’s not really a contest. A 50-liter version comes in under 20 ounces with a full carbon fiber frame, hipbelt, and everything. Nothing else with a real internal frame is within ten ounces of it.

The trick is the frame itself. Zpacks uses a pair of curved carbon fiber stays that bow away from your back, so the pack hangs off your hips with airflow under the frame. It transfers load like a proper framed pack instead of just being a big sack with a foam pad. The fabric is Ultra, the hardware is minimal, and the whole thing is built for the 30-pound-or-less crowd.

What’s the tradeoff? It’s a 19-ounce frame, not a 39-ounce frame. It carries 25 pounds great, 30 pounds fine, and past that it gets floppy. The Durston Kakwa 55 is the smart purchase for most people — around 35 ounces, far more durable, and a lot cheaper — but it’s not the lightest. The SWD Long Haul and Osprey Levity are respectable framed options in the high-20s to low-30s, but they’re still chasing the Zpacks. Nobody is actually chasing it, to be fair. They just happen to also make packs.

Just remember: a 19-ounce pack is only light if you keep the load light. That’s sort of the whole point.