I recently purchased the New High Sierra hydration pack with the two liter water pack.  I bought this in a buy it now auction for $20.96 including shipping, and let me tell you, it was well worth the price!  At $65.00 as a suggested retail price you are getting quite the deal by buying from the ebay store (thesportsmanguide).  The quality and useability of this backpack is amazing!  I personally like the VAPEL(R) mesh air flow padded back.  It creates an air pocket between you and the backpack actually holding the pack away from you as an added body cooling mechanism.  Many other great features of the pack include: an insulated water tube, hidden rain cover in bottom pocket, sternum and waist straps all heavy duty and fully adjustable.  There is also reflective piping down the back and sides so you will be more visible at night, plus the whole pack is made of a heavy duty 600-denier Duralite and ripstop shell.  I have owned another hydration back pack by Jansport and although it is nice I think the New Seirra is a step above.  The size of this pack was also a feature I was pleased with, not to big, not so small.  The actual cubic capacity is not listed anywhere on the tags but the size is listed as 16"x12.5"x6".  I would say you could probably fit two college size text books along with a lunch into the main pocket with room left over in the outer pocket.  All things considered, this is well worth the money if you are looking for a hydro back pack, and if you come across one for such a deal on ebay or anywhere else youjust might consider it.  Thanks for visiting!