The Mr. Heater 4 Horizontal Vent Kit. Meets UL1738. These stainless steel parts are designed to fit the MHU50 or MHU80 Big Maxx Garage Heaters. NOTE:other select parts may be required for your installation needs. Includes:One 3-4" Adapter; One 4 x 36" B-vent Pipe; Two 4 x 24" Vent Pipes; One 4" 90 degree Elbow; Wall Thimble; Roof Flashing; Storm Collar; Vent Cap.