Mr. Heater garage heaters Item#s 173636 and 173637 require direct venting to deal with by-products of combustion. Venting kit meets all standards related to the national fuel gas code. For horizontal mount only. Kit includes: One 4in. Elbow (26-GA) One 3in. to 4in. Connector One 4in. Gas Vent Top Two 4in. x 2ft. Pipe (26-GA) One Adjustable Wall Thimble One 36in. x 4in. B-Vent