The Telescopic Adjustable Underfloor Cavity Vent Extension is the perfect solution for ventilation solutions in homes that have a vertical step of 6 to 7 brick courses. It fits perfectly between the upper and lower parts of the telescopic underfloor ventilator, ensuring a snug fit and optimal air flow. With this product you don't have to worry about gaps or compromised performance: the extension is adjustable and can be tailored to fit just about any space.