Chimney Cowl 180 plug-in 176mm, Flue, Cap, Chimney Pot by windkatcowls.co.uk
This would then have a plug-in 176mm and would fit exactly into the chimney/pot/flue opening. Rain Cowl 180 plug-in 176mm - Silicone - Instructions. - The Rain Cowl is suitable for all single or double walled chimney systems.