Schebler Chimney Systems makes the eVENT prefabricated chimney system for high-efficiency condensing boilers. The UL 1738-listed structure with a 1-inch air gap comes in even and odd sizes from 5 to 48 inches. The eVent is made of corrosion-resistant, 24-gauge AL29-4c stainless steel for extended life. The product features a 1/2-inch turned-out flange that increases pressure arating and eliminates condensate leakeage. Applications include gas-fired appliances listed as Category II, III and IV.