Packs are much like boots there isnt one that fits all. Most of the guys use a 40-50 liter volume top loader that has extension collars for stuff extra bulk inside. Any larger and we run the risk of packing too much.

Many civilian packs are tough these days and they fit the bill without breaking the bank. I personally use a Canadian brand called Mountain Equipment co-op. Decent gear for a good price. The model I use is the Alpine 45.

http://www.mec.ca/Products/product_detai...D=1196738488243



My suggestion would be to try on many and add 30% to your expected load out volume. Fit is everything.

Hound