200/300

200/300 insulated chimneys are designed for the highest-capacity heating appliances. This designation indicates the chimney’s two main dimensions:

200 mm: The chimney’s internal diameter. This is large enough to ensure smooth flue gas removal and strong draft, which is important for larger heating systems.
300 mm: The chimney’s external diameter. This provides enough space for a thick and effective insulation layer, which keeps the chimney’s outer surface cool and safe.