Am a 5'7" 120lb female. Bought s/m, blue. 18 L. This pack adjusts very well for its size. Prompt delivery. Has mesh hip belts, load lifters and side adjustment straps.... rare for this sized pack; you can really customize fit. Have a larger pack for multiple-day trips. Does not come with hydration bladder...but. There are two pockets externally on each side (your right and left) for liquids, shoes or wet gear. Not too large; not too heavy or wide. Nifty rain cover in bottom pocket. Good for extended day hikes, bike rides, and travel. Really like the top, smaller zip pocket for glasses, passport, cash, pencil, keys or smallish items you don't want falling to bottom of pack; place to hang rear red light for safety and hang straps on both front right and left shoulder straps for your shades or glasses. You could carry on plane and tuck under seat. Great fit. Only (small) gripe? When I dial in my hip belts, and clip both sides together, there is a whole lotta left over strap. (perhaps if I wore over my rain gear or jacket fit would be larger? ) Do I cut excess off, let excess dangle, pin excess or... just get annoyed by them?