INCLUDED - Pack of 12 Lap vents. Helps provide airflow and ventilation in the loft space preventing Condensation. DRY LOFT SPACE - Use to increase airflow in the loft space, and prevent condensation. Stops your loft being damp in the winter. And helps release any steam caught in the loft space from bathing / showering. INSTALL - Clip between the felt joins, the vents then allow more airflow in the loft to prevent condensation. SIZE - Each Lap Vent is 280mm, 190mm, 30mm, providing extra airflow to the loft. FIT - Designed to be universal, its between any joists from 350mm to 600mm, Manufacturer: Howsehold