My husband is the army and he uses these all of the time. They are perfect for all sorts of outdoor activities on top of work. I like to use them for running or hiking mostly. This is so easy to use you simply fill the water and then use the connective hose to take a drink. The straps are adjustable of course! I love how the back of this one is so soft and comfortable. It is very important to take the water out and leave to dry after each use because they do mold. I also love that it had has that extra pocket late for addition items you may need (car keys, cell phone, thin snacks, ect. The only complaint my husband and I have is the on/off valve is different from what he gets in the army, and those tend to be a little better but this one is similar to another one I have owned and it still works great. Over all we both love the hyrdoflask!

http://www.amazon.com/Welltop®-2-5LSports-Camouflage-Hydration-Backpack/dp/B018E5VTLG?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o07_s00

I received this product for free in exchange for my honest and unbiased review.