These Ortlieb panniers are fashioned in the style of boating dry bags.  Roll up the bag and its waterproof construction will keep your books, papers, and clothing as dry as when you started off, in any sort of weather.  Or in case of flash floods.  Smart shoulder strap design makes carrying the bag from bike-to-location.  Reflective material on front and back of bag (in mounted position), keeps motorists (and other cyclists) aware of your presence.  You'll be commuting, or ready for a camping trip, in any sort of weather with these bags.