Well thought, there's a belt to maintain the backpack straps when they are not in use, the handles are sturdy and comfortable.
my mechanically tuned djembé 12'' at the skin end so you definitely want this size to fit it, because it's already tight and with the mechanics you need to see larger than the skin.
The foot end is seriously small, so the precious ivory coast djembé I just got won't fit easily while head and height size are ok, if you've got an instrument with a larger foot end stay away.