Nathan fireball running backpack the nathan fireball running backpack is designed for runners wanting minimum interruption in their running stride the backpack keeps water colder with two 12 oz insulated speedshot flasks for the front pockets and is also compatible with a 15l bladder running backpack unisex adults comes with two 120z insulated speedshot flasks with push pull blast valves 15l bladder compatible expandable main zippered pokcets for easy access to your ge