This push-fit twin wall system used for gas, oil and solid fuel appliance installations that can be used as part of an internal or external installation. This twin wall system can be used in whole, or in part to complete a flexible flue liner installation where a masonary chimney is only partially present. For use on solid fuel and gas/oil appliances. eg: woodstoves, gas coal effect fires, oil boiler and any solid fuel appliances. Twin Wall Insulated Chimney parts are secured togrther by using a Locking Band. Make sure that you keep a distance of 60mm from the outside of the flue to any combustible material (wood, plaster board).