Osprey's Viper 9 is designed for cyclists who like to push the limits-packing full day rides into half that time and bringing just enough gear to make it home. . . . 210D Poly Honey Comb, 420HD Packcloth. . Atilon foam framesheet provides optimal mobility while evenly distributing load across entire backpanel. . Biostretch(TM) harness provides an active, contoured fit with optimal ventilation. . Mesh covered ridged foam Airscape(TM) backpanel delivers ventilation. . Removable 20mm webbing ride stabilizing hipbelt. . Dedicated hydration compartment with direct zip access. . Hydraulics(TM) LT 2.5 liter reservoir with magnetic bite valve retention. . LidLock(TM) elasticized attachment system for easy helmet storage. . Blinker light attachment strap. . Stretch mesh harness pocket provides easy access to essentials. . Front zippered stash pocket with head embossed scratch-free lining. . Volume: 549 cu. in. (9L). . 18H x 9W x 7D in. total dimensions. . 1.21 lb. total weight. .