This extension fits into the lower opening at the rear of the Ventilator. It is part of Timloc’s Underfloor Vent System. It is a horizontal rear extension piece that has been designed to be used with the Telescopic Underfloor Ventilator. The specially designed front grille on the Telescopic Underfloor Ventilator must be removed to allow the rear of the vent to the extension. Once you have the required amount of sleeves equip to suit the thickness of your wall, you need to reattach the vermin grill so the end of the sleeve. Fits into the lower rear opening of the telescopic underfloor ventilator to accommodate cavity widths between 50-150mm – or internal walls of more than 100mm thickness, up to a maximum of 200mm. This product is used when the thickness of the wall is larger than 100mm.. Once a section of the Rear Extension is attached to the Telescopic Underfloor Ventilator it will reach 200mm. Each sleeve adds 100mm of length. Features & Benefits Does not restrict airflow through the main telescopic underfloor ventilator Purpose-made accessories eliminate the need for on site modifications Lightweight and easy to handle Durable and totally resistant to decay Robust material Product Specification Added length: 100mm Colour: Black Quantity: 20