Schiedel B Vent flue Vitreous Enamel Connector - 100mm Part of the twin wall gas venting system for residential and small commercial gas appliances with input up to 60 kW. Either as a complete system or in combination with flue blocks or brick chimneys. Must not be used for oil-fired or solid fuel systems. Note that for external runs exceeding 3 metres, BS 5440-1 requires the use of a stainless steel insulated flue. The ICID Flue range meets this requirement. This converts the single skin vitreous enamel flue pipe to B vent twin wall.