Selkirk 16" to 24" Closure Ring (Ultra-Temp / Galva-Temp Large)Selkirk 16" to 24" Diameter, Closure Ring Required to cover the insulation at the top of the chimney if any termination other than Selkirk Round Top is used. All Fuel Chimney Ultra Temp Galva Temp Large For projects where a larger chimney is required, Ultra Temp and Galva Temp Large Diameter are secure, easy to install, and available in 16" to 24". Selkirk UTL and GTL Large Diameters are used for masonry chimney applications. Ultra Temp: 430 Stainless