The category 1 vertical 6-in vent kit provides class 1 single wall B-vent ducting for Mr. Heater Big Maxx and Heatstar unit heaters, ranging from 250, 000 to 400, 000 BTU. Designed for vertical installation only. Kit includes a 6-in gas vent top, a storm collar, an adjustable roof flashing, a 6-in by 26-in B-vent pipe, two 6-in by 24-in 26-GA pipes, a firestop support plate assembly, and a 4-in to 6-in adapter (if needed). Other parts may be required for your specific installation needs. Please check and adhere to all state and local codes before installation. | Mr. Heater 6" Vertical Vent Kit