Instead of combusting heated inside air, all of this combustion air enters the firebox from outside through the outer cylinder. There's not wish the warm glow for a fireplace when it is cold other. The unit measurements are 9.9 x 10.6 x 0.9 inches and weighs 2 extra weight. http://www.Dungdong.com/home.php?mod=space&uid=3152303&do=profile