Shayna "P.C." wrote an answer about JanSport Klamath 68 Backpack - 4200cu in on January 2, 2013
I can put my 4 liter Platypus in it. It sticks out the top of the sleeve if filled all the way but I rarely have more than 3L in it. In this photo all 3 liters of water are in the sleeve.