First this bag is NOT for dogs up to 25lbs maybe 15. Our cavalier king charles is 14lbs and barely fits
Second the bag is designed with metal rods to extend the bag and give your dog room. These rods are difficult to put in place and our 14lb dog knocks them out of place. Theses rods start poking/prodding him and he whelps in pain. So we have to pause our hike and re-adjust. 
Just avoid this bag. Was fooled by the great reviews