This backpack was purchased for my son's Christmas. Being a 7 year old boy and an avid Mountain Biker, I knew it would be the perfect gift. Thankfully, he loved it! The bladder is nice and thick and fits nicely inside the backpack. The mouth peice is very large and difficult to get working, but we've managed to just remove the large plastic peice and attach the open mouth peice in an upright position while he's riding. The bag fits nicely on him and would be comfortable for an adult as well. It is lightweight and has several pockets forstoring items during a hike or ride.