Silvacore Pro by Duraflue Ventilated firestop plate: 5", 6", Silver, Black.Allows air to pass through and therefore vents a void so as to avoid heat build up. See also 3 part ventilated set in Product Addons. This is a twin wall clip together chimney part used to build a new chimney. Twin wall clip together chimney can be as close as 5cm to combustible materials (7cm if passing through a sealed void). No glue or sealants required. When we say 5 or 6 we speak of internal diameter: outer diameter is 7. 5 and 8. 5 (192mm and