Schiedel B Vent flue Adjustable Pipe - 150 x 300mm Part of the twin wall gas venting system for residential and small commercial gas appliances with input up to 60 kW. Suitable for internal and external use, 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 5440-1:2000 requires the use of a stainless steel insulated flue. The ICID Flue range meets this requirement. This is adjustable because it slides over a flue pipe below and straps into place.