There is a reason this is used in the armed forces - CamelBak ArmorBak Hydration Pack - 102 oz/3.1L

Great design, more compact than other 3.0 Liter Hydration Carriers in the market, one of the top two choices for hydration in the US Armed forces along with the Thermobak AB, the quick detach system is great for quickly hooking to the molle on my plate carrier or hiking backback.(this is the only way to connect this model, if your gear isn't molle look into the thermobak AB it has the same molle system and backpack type straps...) I love my armorbak could never use another kit from here on!
Pros: quick detach, capacity, Camelbak quality, compact size for 3L unit
Cons: it can only attach to molle like on a plate carrier or possibly a backpack of the right size, otherwise no light load hiking unless you can find a full back molle harness, bladder is removable though so you could transfer to a cheap carrier seen many for $10-$13

This review was written in the old system and had content requirements that are different than reviews written today.