Description of Gregory Z 55 Backpack With an all-new ventilated Jet Stream™ Suspension, this durable, yet lightweight pack carries like a dream. Thru hikes, lightweight three day weekends, or trips to the crag are just a few places you'll enjoy wearing this fully redesigned classic. Features: Jet Stream™ suspension system Auto.Fit harness system Ventilated, moisture wicking harness and waistbelt system 1/2” 7001 T6 aircraft aluminum hollow stay Weight reducing molded V-beam framesheet Top and side access Expandable front ”Bucket” pocket Secondary front pocket Water resistant top pocket and front pocket zippers Water resistant side access zipper Dual quick access waistbelt pockets 210D HT ”double box” ripstop nylon 210D HT nylon twill S 3050 IN3 / 50 L 3 LBS. 2 OZ. / 1.4 KG M 3350 IN3 / 55 L 3 LBS. 5 OZ. / 1.5 KG L 3660 IN3 / 60 L 3 LBS. 8 OZ. / 1.6 KG