700kms later which is best | Mountainsmith Zerk 40 vs Osprey Aura AG 50

Ultralight compared to traditional - the Mountainsmith Zerk 40 against the Osprey Aura AG 50 - carried side by side for over 700km.

Gordo has been running the Mountainsmith Zerk 40 - a 40L ultralight pack built around running-vest straps and co-designed with thru-hiker The Real Hiking Viking. Kaity carries the Osprey Aura AG 50, a framed pack with Osprey's Anti-Gravity suspension and a full hip belt. For over 5 years we have used both packs all across Australia on multi-day overnight hikes and day hikes and this is how they compare on weight, comfort under load, access on the move and durability + Gordo drills into the good the bad and the ugly of using a fastpack as your everyday adventure pack.

📍Hikes we've used the packs on for this video:
→ Conondale Range Great Walk, Queensland
→ Tabletop Track, Northern Territory
→ Piccanninny Treck, Purnululu National Park, Western Australia
→ Grampians Peaks Trail, Victoria
→ Sections of the Overland Track, Tasmania
→ Freycinet Naitonal Park Great Walk, Tasmania
→ Three Capes Track, Tasmania
and many more day hikes.

💡Tips:
→ The Zerk is at its best on lighter loads - Mountainsmith rates it to ~13kg but I've had it to ~15kgs. Above that, a framed pack like the Aura carries noticeably better.
→ Understand your kit, its bulk and weight before choosing. Your base weight decides between these two packs more than anything else.
→ Try the Aura's hip belt on loaded in store. The fit is the whole point of a traditional pack and I've find that they can be quite annoying if not configured right.
→ The Zerk 40 in this video was from 2021. In 2026 there is an updated Zerk 40 which has a different material and an optional 7L top lid and Loki lumbar pack (sold separately).