"SELKIRK" TYPE B ADJUSTABLE ELBOW 45-60 DEGREE *4" *Type B gas vent *OD = ID + 1/2" *Adjustable *Inner wall aluminum, outer wall galvanized *For gravity draft venting of "listed" LP or natural gas burning appliances *100 million BTU per hr., 500 deg. F max *Appropriate for thru wall where applicable *Not for wall furnaces *UL listed *10 yr warranty *Boxed