This 4 In. vertical ventilation kit can be used with the Heatstar or Big Maxx Indirect Fired Unit Heater for vertical venting. Designed to fit the MHU75, HSU75, MHU80 and HSU80 model unit heaters. Designed for vertical installation only. Allows Category 1 unit/utility heaters to comply to both the Canadian Standard S605 and the US standard UL441. Includes 1 3 In. to 4 In. adapter, 1 4 In. x 36 In. B-vent pipe, 1 4 In. 90 Deg degree elbow, roof flashing, storm collar, vent cap, gas vent firestop spacer. Warning: This product can expose you to chemicals including lead and lead compounds which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information visit www.P65Warnings.ca.gov.