Osprey, one of the biggest names in backpacking, has officially joined the ultralight game. The new ThrULite Pro series comes in 20-, 40-, and 55-litre sizes, and the flagship 55L weighs just 27 ounces (765 grams) — territory usually reserved for boutique brands like Hyperlite Mountain Gear, Zpacks, and Gossamer Gear. The price is $340, undercutting most of those rivals.
The pack was put through months of real-world testing on late-summer and autumn hikes in Maine, including long guiding days over rocky, root-strewn mountain trails. The tester's usual pack is a Hyperlite Southwest 55, so the comparison carried real weight.
The headline finding: comfort. Osprey swapped its usual trampoline back panel and traditional shoulder straps for a running vest-style harness paired with a minimalist frame. The result carries securely and feels more substantial than the sub-two-pound weight suggests, holding up well over long days on rugged terrain. The proprietary NanoFly nylon/UHMWPE ripstop fabric shed light rain effectively, though the reviewer stops short of vouching for it in sustained downpours — a pack liner is still recommended for longer trips.
Storage is mostly well thought out. The tall side bottle pockets have adjustable cinch tops, and a deep rear pocket swallows a rain jacket or other grab-and-go gear. The most usable detail for hikers eyeing their first ultralight pack: Osprey's established warranty and repair programme backs it all up.
Two design gripes stand out. Both hipbelt pockets — one zippered, one elastic — are so small they're barely useful for snacks or a phone, a strange oversight on a pack built for long trail days. And the roll-top closure, which replaces the traditional lid to save weight, is fiddly to use and doesn't compress small loads as tightly as competitors like the Hyperlite offer.
For context, the alternatives: Hyperlite's Southwest 55 costs $399 and weighs 29.3 ounces, Gossamer Gear's Mariposa 60 runs $315 at 34.2 ounces, and Zpacks' Arc Haul Ultra 60L is $399 at a featherlight 22 ounces but with a 40-pound max load.
The takeaway for travellers and trekkers: if you've been curious about ultralight backpacking but put off by niche brands, limited warranties, or stripped-down comfort, Osprey's entry is a genuinely compelling option. It's not perfect — bigger hipbelt pockets and a smarter roll-top would fix most of the complaints — but as a first step into cutting pack weight without sacrificing how it feels on your shoulders, it makes a strong case.
Review pack donated by Osprey; tested across multiple months of hiking and guiding in Maine.
