Osprey Sirrus 36 vs Zpacks Nero Classic 40L

Weight and specs compared for 2026 — and which one to choose.

Zpacks Nero Classic 40L is the lighter option — 931 g lighter than the Osprey Sirrus 36 (76% less weight). If grams matter to you, that is the one to beat.

Spec	Osprey Sirrus 36	Zpacks Nero Classic 40L
Weight	1,220 g · 1.220 kg · 2.69 lb	289 g · 0.289 kg · 0.64 lb
Brand	Osprey	Zpacks
Category	Backpack	Backpack

Osprey Sirrus 36

1,220 g

Women's ventilated 36L pack with AirSpeed back panel.

Full details →

Zpacks Nero Classic 40L

289 g

Frameless ultralight pack in 30L or 40L, built from Dyneema CF fabric. One of the lightest load-carrying packs available for thru-hiking.

Check price Full details →

Osprey Sirrus 36 vs Zpacks Nero Classic 40L: which should you buy?

If saving weight is your priority, the Zpacks Nero Classic 40L wins — at 289 g it is 931 g (76%) lighter than the Osprey Sirrus 36 (1,220 g). That said, the heavier option may justify the extra grams with more capacity, durability or comfort, so weigh the trade-off against how you'll use it.

See where both rank against everything else in this category on the lightest backpack page, or browse the full gear weight database.

More backpack comparisons

Osprey Sirrus 36 vs Salomon ADV Skin 12 Osprey Sirrus 36 vs Zpacks Nero Classic Ultra Backpack Osprey Sirrus 36 vs Zpacks Nero Classic 50L Osprey Sirrus 36 vs Zpacks Nero Classic Backpack Osprey Sirrus 36 vs Zpacks Nero Classic 30L Osprey Sirrus 36 vs Zpacks Nero Classic