The MT900 Ultralight 45+10L is clearly the lightest model in this women's range — 1,316 g for 45 liters (plus a 10L extension) works out to 23.9 g per liter, noticeably better than the heavier MT100 or MT500 AIR. Its classification as an ultralight pack, with thru-hiking explicitly listed among its intended uses, confirms this is built for a lower base weight rather than general-purpose trekking.
An internal frame instead of aluminum stays, plus an AIR concept mesh back panel, save weight without leaving the pack entirely without support. The 100D RS polyamide (recycled nylon) fabric is thinner than on the heavier models in the range, trading some abrasion resistance for lower weight — a typical ultralight compromise.
A padded hip belt with pockets, an integrated rain cover, and hydration bladder compatibility are retained despite the weight cuts. This suits experienced hikers who already have a dialed-in gear list and want to shed pack weight without giving up basic comfort.