We ended up getting the Ace 48 for my son (10), because my daughter (12)got the Ace 50. She wanted blue, he wanted red, and so they are both happy. My son doesn't realize that his red pack, is about 1 pound heavier than his sisters and that's just fine. Typical awesome Osprey design and lots of great features (belt pockets, compression straps, very adjustable height wise (my son is just at the minimum, but carried 15 pounds the first time with not a beep). The new Ace 50 has more adjustable and is lighter, so I think a better buy, though you can't beat the price of the Ace 48 these days. Or the color........
This review was written in the old system and had content requirements that are different than reviews written today.